1. Without warning or announcement
   - unannounced, unheralded

See also: unexpected

• outflow
• outflowing
• outfox
• outgas
• outgeneral
• outgo
• outgoer
• outgoing
• outgrow
• outgrowth
• outguess
• outgun
• outhaul
• outhouse
• outing
• outlander
• outlandish
• outlandishly
• outlandishness
• outlast
• outlaw
• outlawed
• outlawry
• outlay
• outlet