1. Being in effect or operation
   "bus service is in operation during the emergency"
   - operational, operating

See also: operative

• unsupportive
• unsuppressed
• unsure
• unsurmountable
• unsurpassable
• unsurpassed
• unsurprised
• unsurprising
• unsusceptibility
• unsusceptible
• unsuspected
• unsuspecting
• unsuspectingly
• unsuspicious
• unsustainable
• unswayed
• unsweet
• unsweetened
• unswept
• unswerving
• unswervingly
• unsworn
• unsyllabic
• unsyllabled
• unsymbolic