Definition of: tailgate

(tāl′gāt′) noun
1. A hinged or vertically sliding board or gate closing the back end of a truck, wagon, etc. Also tail·board (tāl′bôrd′, -bōrd′).
2. One of the gates at the lower level of a canal lock.
—v.t. & v.i. ·gat·ed, ·gat·ing U.S. Slang To drive too close behind for safety: impatient drivers tailgating in a no–passing zone.