eruptive / irruptive are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
eruptive: (adjective) producing or characterized by eruptions. (adjective) actively spewing out lava.
irruptive: (adjective) of igneous rock that has solidified beneath the earth's surface; granite or diorite or gabbro.
eruptive: ih·r·AH·p·t·ih·v
irruptive: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)