1. the waste matter separated from metals during the smelting or refining of ore
Usage: technical

1. to criticize harshly or speak badly about someone
Usage: British; informal

Examples

• The steel mill produced tons of slag as a byproduct.
• Workers removed the slag from the furnace after each batch.
• The slag heap grew larger each day at the mining site.
• She slagged off her former boss in the interview.
• Don’t slag him just because he made one mistake.
• The critics really slagged the new movie.