Entry 1 sense Webster, 1913 Spinnaker /(spĭn"nȧ*kẽr)/ · Spin·na·ker · IPA /ˈspɪnəkɚ/ 01 n. A large triangular sail set upon a boom, -- used when running before the wind. 1. A large triangular sail set upon a boom, -- used when running before the wind.(Naut.)