Meaning : Engaged in or accustomed to close observation.
Example :
Caught by a couple of alert cops.
Alert enough to spot the opportunity when it came.
Constantly alert and vigilant, like a sentinel on duty.
Synonyms : alert
Watchful ka meaning, vilom shabd, paryayvachi aur samanarthi shabd in Marathi. Watchful ka matlab kya hota hai?