Crossword clues for the word: NOXIOUS The word NOXIOUS has appeared as an answer to at least 7 crossword clues on different crossword puzzles. Crossword clues for NOXIOUS Showing 1 to 7 of 7 results Clue(s) Harmful Harmful to one's health Like substances in city air Perhaps brave to swap sides after earlier refusal is harmful Physically destructive Poisonous Poisonous or harmful — gases?