A substance that undergoes a rapid chemical change (with the production of gas) on being heated or struck.
Any material capable of a sudden release of energy and the rapid formation of a large volume of gas, leading when compressed to the development of a high-pressure wave (blast).

ETYM Cf. French explosif.
1. Liable to lead to sudden change or violence; SYN. volatile.
2. Sudden and loud.
3. Tending or serving to explode or characterized by explosion or sudden outburst.