1. To make any substitution in a game, without the knowledge of
one’s opponents, as to substitute
crooked dice or
marked cards; to bring an
expert swindler into a game with unsuspecting adversaries; to pass off a master as an amateur; to enter
a horse in a race after altering his identification
marks in order to fake the odds, 2. To substitute an outsider for an absent member of a gang; to bring in a specialist to execute a difficult assignment; to force (oneself) into a
desirable position in a game or racket.
“We got to ring in a good wheelman (chauffeur) on this score (robbery). The town is lousy
with (teeming with) squad cars (police squad cars)." 3. To report by telephone, as a
policeman on beat; to
punch a clock, as a
watchman.
- american underworld dictionary - 1950