Reef \Reef\, v. t. [imp. & p. p. {Reefed} (r[=e]ft); p. pr. & vb. n. {Reefing}.] (Naut.) To reduce the extent of (as a sail) by roiling or folding a certain portion of it and making it fast to the yard or spar. --Totten. {To reef the paddles}, to move the floats of a paddle wheel toward its center so that they will not dip so deeply.