Definition of "unpremeditated"
Performed, but not planned or thought out in advance; extemporaneous, but not unintentional.
Quotations
Hail to thee, blithe spirit! / Bird thou never wert, / That from heaven, or near it, / Pourest thy full heart / In profuse strains of unpremeditated art.
1820 June (date written), Percy Bysshe Shelley, “To a Skylark”, in Prometheus Unbound […], London: C[harles] and J[ames] Ollier […], published 1820, stanza 1, page 201