bench mark, benchmark - a surveyor's mark on a permanent object of predetermined position and elevation used as a reference point

landmark - a mark showing the boundary of a piece of land

lubber line, lubber's line, lubber's mark, lubber's point - a fixed line on a ship's compass indicating its heading

criterion, standard, touchstone, measure - a basis for comparison; a reference point against which other things can be evaluated; "they set the measure for all subsequent work"

target, mark - a reference point to shoot at; "his arrow hit the mark"

white line - a white stripe in the middle of a road to mark traffic lanes

indicator - a signal for attracting attention

buoy - bright-colored; a float attached by rope to the seabed to mark channels in a harbor or underwater hazards