Noun

1. the univalent anion, O₃^{-, derived from ozone}
2. any dark red salt of this anion and a metal
3. any of a number of explosive organic compounds containing a -O-O-O- group
4. any of a class of heterocycles, containing two carbon atoms (in positions 3 and 5) and three oxygen atoms (in positions 1, 2 and 4) produced by the reaction of ozone with a carbon to carbon double bond; the 1,2,4-trioxolanes