Entry 1 sense Webster, 1913 Sinusoidal /sīn'-əs-oidˌ-əl/ · Si·nus·oid·al · IPA /ˌsaɪnəˈsɔɪdəl/ 01 a. Of or pertaining to a sinusoid; like a sinusoid. 1. Of or pertaining to a sinusoid; like a sinusoid.(Geom.)