noun
surprise concert; guerrilla live
A live performance, typically by a musician or band, announced with little or no advance notice, often in an unexpected location. The term is wasei-eigo from English 'guerrilla' and 'live'.
wasei-eigo (Japanese-coined English), from guerrilla live
人気バンドが渋谷でゲリラライブを行った。
The popular band held a surprise concert in Shibuya.
ゲリラライブの情報はSNSで突然発表された。
Information about the guerrilla live was suddenly announced on social media.