Explanation of Jam

The term ‘jam’ is common usage slang term for an all-in bet made as the aggressor. 

For information on when it is strategically correct to get the stacks in see the glossary entry under all-in.

Example of Jam used in a sentence -> We 4bet preflop then called our opponent’s 5bet jam with our pocket Queens.

See Also 

Shove, All-in