adjective
1Not precipitated; especially (Chemistry) not deposited as a solid product, remaining in solution.
2Not (overly) rushed, hasty, or impetuous; unhurried, leisurely.
3Having no immediate or apparent cause; unprompted, unprovoked.
Origin
Mid 17th century; earliest use found in Robert Boyle (1627–1691), natural philosopher.
Are You Learning English? Here Are Our Top English Tips