Nautical. a square mainsail.
the principal dish or course of a meal, typically including meat or fish.
Origin of main course
First recorded in 1505–15
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for main course
Towards midnight of the 20th June, the wind increased so much, that we had to lay our ship a-try all night under her main-course.
The jib and flying jib were also taken in, and a little later the main-course and the mizzen-course.At the Fall of Port Arthur|Edward Stratemeyer
British Dictionary definitions for main course
the principal dish of a meal
nautical a square mainsail
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012