What is Coarse ?
Coarse is (adj) 1. not fine, not small coarse grains of sand a coarse net 2. rough, not refined He gave a coarse laugh. He could hear her coarse voice booming down the corridor. 3. (of words or gestures) rude He made a coarse gesture and walked out. Don’t make any coarse remarks in front of my mother. (NOTE: coarser – coarsest. Do not confuse with course.)
source: Easier English, Student Dictionary Upper Intermediate Level