three-square
1 of 2adjective
: having an equilateral triangular cross section —used especially of a file
three-square
2 of 2noun
1
or less commonly three-square rush [so called from the triangular stems] : any of various rushes of the genus Scirpus
especially : chairmaker's rush
2
: a three-square file
Word History
Etymology
Adjective
Middle English thre sqware having three equal sides, from three, thre three + sqware, square square