1. a rhythm pattern where the percussive bass takes place on every downbeat. Common in house, trance, other forms of techno, disco, etc.
it is the opposite of a breakbeat, where the percussive bass can be anywhere, but is normally not on beats 2 and 4, and rarely on 3.
2. refers to a 4 speed transmittion with the shifter on the floor (as opposed to the dash or the column)
2. John wrecked the four-on-the-floor transmittion in his car by going 80 MPH and then quickly shifting into reverse.