Definitions of volatile:

• noun:   a volatile substance; a substance that changes readily from solid or liquid to a vapor

  Example: "It was heated to evaporate the volatiles"

• adjective:   evaporating readily at normal temperatures and pressures

  Example: "Volatile oils"

• adjective:   tending to vary often or widely

  Example: "Volatile stocks"

• adjective:   liable to lead to sudden change or violence

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

• adjective:   marked by erratic changeableness in affections or attachments

  Example: "A flirt's volatile affections"