ˌ ̷ ̷ ̷ ̷ˈhē]drən sometimes ]ˌdrän or chiefly Brit ˈhe] noun
( plural tetrahedrons or tetrahe·dra -drə\)
Etymology: New Latin, from Late Greek tetraedron, neuter of tetraedros having four faces, from Greek tetra- + hedra seat, face — more at sit
1. : a polyhedron of four faces
2. : an object having the form of or suggesting a tetrahedron: as
a. : caltrop 2a
b. : three logs or lengths of steel bolted or lashed together and used as an obstacle
c. : a large concrete block of tetrahedral shape used especially in constructing or strengthening revetments — compare tetrapod 3
d. : a large wind-indicating device used on airfields and consisting of a frame covered with airplane cloth and pivoted so that the pointed end indicates the wind direction
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