Synonyms: urgent, exigent, pressing, imperative

These adjectives mean compelling immediate attention. 

• Urgent often implies that a matter takes precedence over others:
  "My business is too urgent to waste time on apologies" John Buchan. 
• Exigent and pressing suggest an urgency that requires prompt action:
  "When once disease was introduced into the rural districts, its effects appeared more horrible, more exigent, and more difficult to cure, than in towns" Mary Shelley.
  "The danger now became too pressing to admit of longer delay" James Fenimore Cooper. 
• Imperative implies a need or demand whose fulfillment cannot be evaded or deferred:
  The necessity for preventing war has become imperative.