Usually used in Guitar Hero, a full combo is when someone hits every note in a song and doesn't strum any extra notes. It is usually abbreviated as FC.
No one will ever full combo Jordan, except maybe HellAshes.
A full combo is a rhythm videogame term in which the player successfully hits all of the notes of a song in succession.
This term is most commonly used in games such as Guitar Hero, Rock Band, DDR, and Beatmania IIDX.
"Through the Fire and Flames on Guitar Hero III has been full comboed! I thought I would never see it happen!"
"He is willing to bet that you can't full combo Mei on Beatmania IIDX!"