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 ().
Etymology: ME f. OF intrusion or med.L intrusio (as INTRUDE)
Useful english dictionary. 2012.