1.Definition: evaporating readily at normal temperatures and pressures

"Volatile oils", "Volatile solvents"

2.Definition: liable to lead to sudden change or violence

"A volatile situation with troops and rioters eager for a confrontation"

Related Adjective(s):explosive

3.Definition: marked by erratic changeableness in affections or attachments

"A flirt's volatile affections"

Related Adjective(s):fickle

4.Definition: tending to vary often or widely

"Volatile stocks", "Volatile emotions"