adjective.
Given to capricious or unstable behavior.
adjective.
Characterized by irresponsible or silly behavior.
adjective.
Easily excited; skittish.
The Century Dictionary and Cyclopedia
Indulging in flights or sallies of imagination, humor, caprice, etc.; given to disordered fancies and extravagant conduct; volatile; giddy; fickle; capricious; slightly delirious; wandering in mind.
Fleeting; swift; transient.
the GNU version of the Collaborative International Dictionary of English
adjective.
Fleeting; swift; transient.
adjective.
Indulging in flights, or wild and unrestrained sallies, of imagination, humor, caprice, etc.; given to disordered fancies and extravagant conduct; volatile; giddy; eccentric; slighty delirious.