trigonum
trĭgōnum, ī, n. , triangle : Varro L. 7, 95 ; Gell. 2, 21, 10 ; Col. Rust. 5, 10, 13.
Trigōnum
(τρίγωνον). (1) A triangular piece of marble or tiling used in laying a mosaic pavement. (See pavimentum.)
(2) A musical instrument, triangular in shape.