n. 25B6; noun
the bottom of the stairs : FOOT, lowest part, lowest point, base; foundation, substructure, underpinning.
the bottom of the car : UNDERSIDE, underneath, undersurface, undercarriage, underbelly.
the bottom of Lake Ontario : FLOOR, bed, depths.
the bottom of his garden : FARTHEST POINT, far end, extremity.
the bottom of his class : LOWEST LEVEL, lowest position.
(Brit.) I've got a tattoo on my bottom : REAR (END), rump, seat; buttocks, cheeks; informal behind, backside, BTM, sit-upon, derrière; Brit. informal bum, botty, jacksie; N. Amer. informal butt, fanny, tush, tail, buns, booty, heinie; humorous fundament, posterior, stern; Anatomy nates.
police got to the bottom of the mystery : ORIGIN, cause, root, source, basis, foundation; heart, kernel; reality, essence.
top, surface.
25B6; adjective she sat on the bottom step : LOWEST, last, bottommost; technical basal.
top.
25A0; from top to bottom THOROUGHLY, fully, extensively, completely, comprehensively, rigorously, exhaustively, scrupulously, meticulously.