This is when a modern band gets permission from an old-school band to do a cover of a good song. The new band fucks it up BADLY, and kids today eat the shit MTV feeds them and think it's cool. Then they say the old song "is gay," when in fact the old song is superior and not shittified.
So, the word fucover is a contraction of "fuck" and "cover".
Examples of fucovers:
He Blinded Me With Science (rather than She Blinded...)
What I Like About You (originally by the Romantics)