Definition of jam:
(n) :
a sweet mixture of fruit boiled with sugar and allowed to
set, often spread on bread or toast or used in
jam tarts;
Blockage,
congestion; as a traffic jam, paper jam
"i'm in a bit of a jam right now. Can you help me out?"
(v) :
to block or confuse a broadcasted signal; to throw a pitch at or near the batter's hands
"jones was jammed by the pitch."