A phrase far too overused by people who play Team Fortress 2. They spam it when they do not need to be healed because they are either:
-trying to get the medic away from healing a person they do not like
-a spy looking for achievements or a free backstab
-plainly an asshole
-a suicide player who wants a spawn that lasts longer than 30 seconds.
This can lead to people muting everyone on their team, turning off their speakers, quitting, or just switching classes. These can lead to miscommunications and no healer classes on the team.
Thus, those who spam MEDIC!! are really just trying to get themselves killed.
You pick a Medic class, not knowing what's about to happen.
Spy disguised as a Sniper: MEDIC!! MEDIC!! MEDIC!!