unanticipated (adj.)

• abrupt
• electrifying
• extraordinary
• hasty
• headlong
• impetuous
• improbable
• impulsive
• out-of-the-way
• precipitant
• precipitate
• precipitous
• quick
• shocking
• speedy
• startling
• sudden
• surprising
• swift
• unannounced
• unexpected
• unforeseeable
• unforeseen
• unheralded
• unlooked-for
• unpredictable
• unpredicted