ˌəs(h)chəˈlāshən noun
( -s )
Etymology: Medieval Latin ustulation-, ustulatio, from Latin ustulatus (past participle of ustulare to burn slightly, scorch, from assumed Latin ustulus slightly burned, from Latin ustus, past participle of urere to burn) + -ion-, -io -ion
1. : the action of burning or searing
2. : an operation formerly used in chemistry of expelling one substance from another (as sulfur from an ore) by heat in a muffle