concave shape

Từ điển WordNet v3.1 - WordNet Dictionary

noun

a shape that curves or bends inward
• Syn:
concavity, incurvation, incurvature
• Derivationally related forms:
incurvate (for: incurvation), concave (for: concavity)
• Hypernyms:
solid
• Hyponyms:
dome, pit, fossa, recess, recession,
niche, corner, bowl, trough, scoop, pocket,
depression, impression, imprint, cup, indentation, indenture