1. A mass of people or objects crowded together; also, the pressure from a crowd; a crush; as, a jam in a street; a jam of logs in a river.
2. An injury caused by jamming.
a preserve of fruit boiled with sugar and water; as, raspberry jam; currant jam; grape jam. Jam nut. See Check nut, under Check. Jam weld, a butt weld. See butt.
Origin: Prob. Fr. Jam, v.; but cf. Also ar. Jamad ice, jelly, jamid congealed, jamd congelation, ice.
(Science: chemical) see jamb.