(1):

(n.) An extension of geological beds above and beyond others, as in a conformable series of beds, when the upper beds extend over a wider space than the lower, either in one or in all directions.

(2):

(n.) The lapping of one thing over another; as, an overlap of six inches; an overlap of a slate on a roof.

(3):

(v. t. & i.) To lap over; to lap.