Definition of unpremeditable in English:
unpremeditable
adjective ˌʌnprɪˈmɛdɪtəbl
That cannot be premeditated; impossible to anticipate or foresee.
Origin
Mid 18th century; earliest use found in Laurence Sterne (1713–1768), writer and Church of England clergyman. From un- + premedit- + -able.