• adjective:   highly or violently reactive

  Example: "Sensitive and highly unstable compounds"

• adjective:   disposed to psychological variability

  Example: "His rather unstable religious convictions"

• adjective:   lacking stability or fixity or firmness

  Example: "Unstable political conditions"

• adjective:   subject to change; variable

  Example: "Everything was unstable following the coup"

• adjective:   affording no ease or reassurance
• adjective:   suffering from severe mental illness

Related words...