(n)stone, pit, endocarpthe hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed“you should remove the stones from prunes before cooking”
(n)Hell, perdition, Inferno, infernal region, nether region, pit(Christianity) the abode of Satan and the forces of evil; where sinners suffer eternal punishment“Hurl'd headlong...To bottomless perdition, there to dwell” (John Milton), “a demon from the depths of the pit”, “Hell is paved with good intentions” (Dr. Johnson)
(v)pit, oppose, match, play offset into opposition or rivalry“let them match their best athletes against ours”, “pit a chess player against the Russian champion”, “He plays his two children off against each other”