Video shows what allyl isothiocyanate means. A pungent compound, C3H5NCS, obtained from the seeds of black mustard, or prepared synthetically; sometimes known as mustard oil; it is mildly toxic and is used as an animal repellent, etc.. Allyl isothiocyanate Meaning. How to pronounce, definition audio dictionary. How to say allyl isothiocyanate. Powered by MaryTTS, Wiktionary