OXFORD DICTIONARY
preen, v.tr. & refl.
1 (of a bird) tidy (the feathers or itself) with its beak.
2 (of a person) smarten or admire (oneself, one's hair, clothes, etc.).
3 (often foll. by on) congratulate or pride (oneself).
preen gland a gland situated at the base of a bird's tail and producing oil used in preening.
preener n.
ME, app. var. of earlier prune (perh. rel. to PRUNE(2)): assoc. with Sc. & dial. preen pierce, pin
THESAURUS
preen
adorn, array, beautify, bedeck, bedizen, blazon, brush up, clean, color, dandify, deck, deck out, decorate, dizen, doll up, dress, dress up, embellish, emblazon, embroider, enrich, fettle, fig out, fix up, furbish, garnish, grace, groom, gussy up, manicure, ornament, paint, pique, plume, prank, prank up, prettify, primp, primp up, prink, prink up, redecorate, redo, refurbish, set off, set out, smarten, smarten up, spruce up, titivate, trick out, trick up, trim