mutability in life or nature (especially successive alternation from one condition to another)
a variation in circumstances or fortune at different times in your life or in the development of something; "the project was subject to the usual vicissitudes of exploratory research"
having the function of uniting a group of similar things; "the Democratic Party is an umbrella for many liberal groups"; "under the umbrella of capitalism"
a formation of military planes maintained over ground operations or targets; "an air umbrella over England"
a lightweight handheld collapsible canopy
covering or applying simultaneously to a number of similar items or elements or groups; "an umbrella organization"; "umbrella insurance coverage"
difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge; "the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography"
requiring more than usually expected or thought due; especially great patience and effort and skill; "found the job very demanding"; "a baby can be so demanding"
harshly uninviting or formidable in manner or appearance; "a dour, self-sacrificing life"; "a forbidding scowl"; "a grim man loving duty more than humanity"; "undoubtedly the grimmest part of him was his iron claw"- J.M.Barrie