/kos'teuh noh"euhn, kaw'steuh-/ , n.
1. a family of eight languages, now extinct, spoken by American Indian peoples of coastal California: part of the Penutian stock.
2. any of the speakers of these languages, who formerly inhabited the coast and adjacent river valleys from San Francisco Bay south to Monterey Bay and Point Sur.
adj.
3. of or pertaining to Costanoan or the Costanoans.
[ costano coast dweller ( cost ( a ) COAST, shore + -ano -AN) + -AN ]