Crossword clues for the word: MUSTARDGAS The word MUSTARDGAS has appeared as an answer to at least 9 crossword clues on different crossword puzzles. Crossword clues for MUSTARDGAS Showing 1 to 9 of 9 results Clue(s) Chemical warfare agent Chemical weapon Chemical weapon of WWI Outlawed chemical weapon W.W. I horror Weapon introduced in 1917 World War I weapon WW1 chemical agent WWI chemical warfare weapon