A song that is found exclusively on an album and was never released as a single. Sometimes filler, sometimes under-appreciated, sometimes well-known and equally amazing, album cuts are what fill the spaces between the singles you may have initially bought the album for.
"Do you know that song by Lynyrd Skynyrd, "Tuesday's Gone"?"
"Nah man, never heard of it. I know Free Bird though but everyone knows that haha"
"Well it was off their first album that Free Bird was on -- its an album cut. I think its the second or third song."