Source : Webster's Revised Unabridged Dictionary (1913)

Jam \Jam\, n. [Prob. fr. jam, v.; but cf. also Ar. jamad ice,
   jelly, j[=a]mid congealed, jamd congelation, ice.]
   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} (Forging), a butt weld. See under {Butt}.