n. & v.
n. 1 a device, esp. a brace or band of iron etc., for strengthening other materials or holding things together. 2 a device for immobilizing an illegally parked car.
v.tr. 1 strengthen or fasten with a clamp. 2 place or hold firmly. 3 immobilize (an illegally parked car) by fixing a clamp to one of its wheels. clamp down 1 (often foll. by on) be rigid in enforcing a rule etc. 2 (foll. by on) try to suppress. clamp-down n. severe restriction or suppression.
[ ME prob. f. MDu., MLG klamp(e) ]