Noobcoil refers to the world of warcrafts warcrafts warlocks ability; Deathcoil. Deathcoil Causes the enemy target to run in horror for 3 sec and causes 244 Shadow damage. The caster gains 100% of the damage caused in health.
The reason why people call it Noobcoil is because the Warlock class is a very easy class to play. For PvP (player vs player) the warlocks always cast deathcoil and fear right after, thus spamming DoTs (Damage over time) right after.