posh

Concise Oxford English Dictionary © 2008 Oxford University Press:
posh /pɒʃ/ informal

▶adjective

• 1 elegant or stylishly luxurious.

• 2 chiefly Brit. upper-class.

▶adverb Brit. in an upper-class way. ▶verb (posh something up) Brit. smarten something up.

– derivatives
poshly adverb,
poshness noun.

word history: Posh is first recorded in the early 20th century. Its origin is unknown: it may come from the obsolete thieves' slang word posh, which meant either ‘money’ or ‘a dandy’. There is no basis for the popular theory that posh is an acronym of port out starboard home, referring to the choice of more expensive berths, out of the heat of the sun, on ships between England and India.