n. 1 the act or an instance of intruding. 2 an unwanted interruption etc. 3 Geol. an influx of molten rock between or through strata etc. but not reaching the surface. 4 the occupation of a vacant estate etc. to which one has no claim. 5 Phonet. the addition of a sound between words or syllables to facilitate pronunciation, e.g. the r in saw a film ().
[ ME f. OF intrusion or med.L intrusio (as INTRUDE) ]