n. & v.
--n.
1. (often foll. by on, against) the action of one body coming forcibly into contact with another.
2 an effect or influence, esp. when strong.
--v.tr.
1. (often foll. by in, into) press or fix firmly.
2 (as impacted adj.) a (of a tooth) wedged between another tooth and the jaw. b (of a fractured bone) with the parts crushed together. c (of faeces) lodged in the intestine.
Derivatives:
impaction n.
Etymology: L impact- part. stem of impingere IMPINGE