When a skilled player, or at least, a player who thinks they are skilled, but may or may not actually have skills, is losing horrendously. They then state the phrase "teamfail," often used in conjunction with "omg," or in more extreme cases, "omfg noob team gtfo." Stating this implies that they believe that they are trying their best to win, but their team sucks so much that despite their best efforts, they are still losing. However, it usually is just an excuse for having a bad kdr.
Score (to 5)- Red: 4 Blue: 0
ADpr0: (kdr 12-9, 2 captures) lol blue sux
leetmaster1337: (kdr 16-19) omg teamfail
ADpr0: nice kdr leet
leetmaster1337: its not my fault these noobs suck so much than cant even protect me when i have the flag omfg
ADpr0: yeah wateva nub