Spike

To Spike is to cause a large influx of something (like a spike in a curve). Spiking usually refers to spike damage, but can refer to spike healing or occasionally spike energy.

Spike Damage
A spiker is a player who inflicts massive amounts of damage to a single target in a short period of time, with the goal of taking them down quickly. This is in contrast with a Nuker, whose objective is to deal large amounts of damage to multiple targets over a period of time. A nuker overwhelms the opposing healers' energy supply, while a spiker would overwhelm the healers' immediate healing capabilities. Spikers usually focus on taking down vital opponents, such as restoration Ritualists and Monks, and caster professions in general.

PvP spikes
Spiking first came into widespread use with teams of elementalists, typically Air Magic specialists, who all bombarded the target with a single, high damage spell. Since then the metagame has produced many other spikes over the years, and some worthy of mention are:
 * Ranger spikes, which used the Ranger profession, combining Dual Shot with either Punishing Shot, Savage Shot, or less commonly Quick Shot. A Necromancer or Mesmer/Necromancer using Order spells (like Order of Pain) was added to greatly increase the damage of the spike.
 * Caster spikes, which use spike skills from all caster professions. Necromancer skills such as Shadow Strike, Vampiric Gaze and other similiar Blood Magic skills, Elementalist skills like Obsidian Flame and Invoke Lightning are often used in spikes as well. Mesmers also suit well as spikers, as their Fast Casting reduces casting time of spells and damage-dealing skills of Mesmer profession are armor-ignoring. Ritualists also possess few high-damage spells (like Channeled Strike) in Channeling Magic attribute.
 * Para spikes, which use the Paragon profession, combining high damage spear attacks such as Spear of Lightning and offensive Buffs such as Anthem of Flame and "Go for the Eyes!".

Spikers are popular in PvP because they can quickly kill opponents, weakening the opponents attack and healing capabilities. As the match goes on and players accrue death penalty, they become more susceptible to spiking, creating a slippery slope effect for the opposing team. Also, because of the relatively small number of skills one must devote to spiking, there is much room left over for defensive skills. For example, an Air Elementalist could bring Lightning Orb and Lightning Strike to spike with, then use the rest of his skill bar for skills such as Blinding Flash, Ward Against Melee and Gale.

PvE spikes
Spiking can also occur in PvE. Some Bosses are capable of dealing in excess of 200 damage in a single spell or attack, and this works just like a spike in PvP. In Hard Mode, damage is increased and many bosses will be able to kill a player in a single hit. Ritualists are particularly adept at countering PvE spikes (see below). Some of the Bosses capable of dealing this much damage are Sskai, Dragon's Birth, Birneh Skybringer, Korr, Living Flame and Orosen, Tranquil Acolyte to name but a few. Multiple hit attacks are particularly lethal in Hard Mode, and bosses such as Wing, Three Blade can destroy an entire party in seconds if they are not properly prepared. Molotov Rocktail can wipe a whole party in one attack in HM.

Counters

 * The best way to counter a spike build is by using interrupts or knockdowns. This will reduce the total damage from the interrupted spike chain, and possibly end the spike chain prematurely. Additionally, interrupting a spike may cause the spiking team to lose concentration and hinder the ability to prepare for another spike. Skills such as Gale, Mind Shock, Cry of Frustration, Leech Signet, Distracting Blow, or other interrupts can be used to disrupt a spike.
 * Protection Prayers are a good neutralizer to spike damage. They contain spells that limit damage to allies like Protective Spirit, Life Bond and Life Barrier as well as spells that deflect some or all damage such as Reversal of Fortune and Mark of Protection. Spirit Bond is also an effective counter to spikes, and Guardian and Aegis are used as counters to melee and ranged attack spiking.
 * Infuse Health, which, with its 1/4 second activation time and large heal, can often be cast in midspike with a big enough heal to outlast the spike. This monk equipped and using this skill should be well-protected, because once the spiking team realizes what is happening they will likely focus on the "infuser."
 * In GvG one can also split against a spike team. Because most spikes builds require all of the offense to be present to score kills, they will only be able to engage one of your split teams at a time. This will leave your other group free to run flags or kill NPCs without hindrance.
 * Ritualists are also good to counter spikes. Skills such as Union and Shelter can absorb a large portion of a spike, while fast healing spells such as Spirit Transfer and Wielder's Boon can quickly heal a victim in the middle of a spike.
 * Paragons can also be very effective for spike counters with skills such as Angelic Bond, Angelic Protection and Defensive Anthem.
 * Wail of Doom can be effective in reducing the damage output of a spike.

Spike Healing
Spike Healing is healing large amounts in a single spell. In PvP spike healing is most often used to counter spike damage. The most common PvP spike heal is Infuse Health. On a common infuser in PvP, this will usually heal for around 300 health (including Divine Favor).

In PvE, Infusing is generally overkill, and the preferred spike heal is Heal Other or Word of Healing. This is commonly used when one party member takes more damage than expected.

Spike Energy
Spike Energy is a term rarely used anymore. In the past, spike energy came from the necromancer elite Blood is Power, which provides a large energy boost whenever it is needed.

Spike energy is no longer common because of stronger energy management skills. In particular, the Paragon profession has access to multiple party-wide energy management skills like "Never Give Up!" and Aria of Zeal.