From The Collaborative International Dictionary of English v.0.48 [gcide]:
Bas-relief \Bas`-re*lief"\, n. [F. bas-relief; bas low + relief
raised work, relever to raise: cf. It. bassorilievo.]
Low relief; sculpture, the figures of which project less than
half of their true proportions; -- called also bass-relief
and basso-rilievo. See Alto-rilievo.
[1913 Webster]