What is another word for "exigent"?

Roget's Thesaurus (1911) lists these synonyms for "exigent": able, absorbing, ask, call, cannot, case, charge, claim, command, create, crying, death, deficiency, demand, desiderate, desideratum, desire, destitute, dispense, essential, essentiality, exaction, exigency, for, have, imperative, indispensability, indispensable, injunction, instant, lack, life, lose, make, mandate, matter, necessarily, necessary, necessitate, necessity.