凹 āo, wā — concave; hollow; sunken 凹 āo wā Level 1 · Common HSK 7-9 #260 āo ao1 Basic definition adjective concave; hollow; sunken e.g 凹下凹陷凹透镜 Detailed explanation adjective concave;hollow;sunken;dented e.g 凹面 凹岸 · 凹洼 · 凹地 · 凹处 wā wa1 Basic definition noun (old/local) hollow; depression (in place names) e.g 核桃凹山凹 同“洼”（用于地名）。 e.g 核桃凹 Related words 凹陷 āo xiàn hollow; sunken; depressed 凹凸 āo tū concave-convex; uneven; rugged 凹版 āo bǎn an intaglio plate; a gravure plate 凹面 āo miàn concave surface 凹镜 āo jìng a concave mirror; a converging mirror 凹下 āo xià hollowed; sunken 凹透镜 āo tòu jìng concave lens 核桃凹 hé táo wā a hollow named Hetao (place name) 山凹 shān āo a mountain hollow; a dip in the hills