op·por·tun·is·tic 
(ŏp′ər-t-nĭstĭk, -ty-)
(ŏp′ər-t-nĭstĭk, -ty-)adj.
Taking immediate advantage, often unethically, of any circumstance of possible benefit.
- one of these days
- one of those days
- one-on-one
- one-piece
- onerous
- onerously
- onerousness
- oneself
- one-shot
- one-sided
- one-sidedly
- one-sidedness
- Onesies
- one-size-fits-all
- (one's) level best
- one's level best
- (one's) lips are sealed
- one's lips are sealed
- (one's) own man
- one's own man
- (one's) own woman
- one's own woman
- one's self
- one-step
- one-stop