What is a Lock in WoW? World of Warcraft Terms

If you have played more than a few hours of World of Warcraft and you’ve most likely heard the term “lock” thrown around a lot. Against common sense, this doesn’t not usually refer to a locked door or something of that nature. Instead it is an abbreviation for the character class of warlock. You may see people use it as part of a phrase such as “lock summon”, which means to use a warlock to summon an absent party member.
Ever wonder what a "Lock" is?