As a Noun: 1. Something that happens unexpectedly or without warning. As a Verb or Adjective: 1. To happen suddenly or as a surprise. English = (be) unexpected. 2. To appear in a place unexpectedly or to attend an event unexpectedly or without having been invited. Idiomatic English = show up, pop up. As Modifier: 1. Used next to a verb to mean the action happens suddenly and as a surprise. English = unexpectedly.