adj.
(followed by `to' or `of') lacking conscious awareness of; "oblivious of the mounting pressures for political reform"; "oblivious to the risks she ran"; "not unmindful of the heavy responsibility"
adj.
happening by chance or unexpectedly or unintentionally ; "with an inadvertent gesture she swept the vase off the table"; "accidental poisoning"; "an accidental shooting"
adj.
engaged in or accustomed to close observation; "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"