make up off top one's head

Related

Adjectives:

air-built, air-drawn, bucolic, chimerical, chthonic, commentitious, creative, demiurgic, enthusiastic, excogitous, extravagant, fabulous, fairy, fairylike, fanatic, fanciful, fancy, fantastical, fertile, fictive, flighty, haptic, high-flown, ideal, illusory, imaginary, imaginative, imagined, imagining, implicit, in the clouds, inventive, legendary, mythic, mythological, notional, oneiric, oneirotic, original, pastoral, pretend, quixotic, romantic, supermundane, unreal, unsubstantial, utopian, visile, visionary, whimsical