The Collaborative International Dictionary of English v.0.48:

Irruptive \Ir*rup"tive\, a.
   Rushing in or upon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

irruptive
    adj 1: of igneous rock that has solidified beneath the earth's
           surface; granite or diorite or gabbro [syn: irruptive,
           plutonic]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "irruptive":
   advancing, assailing, assaulting, attacking, charging, driving,
   entering, in, inbound, incoming, incursionary, incursive,
   inflooding, inflowing, ingoing, ingressive, inpouring, intrusive,
   invading, invasionary, invasive, inward, inward-bound, thrusting