Source : Webster's Revised Unabridged Dictionary (1913)

Underwriter \Un"der*writ`er\, n.
   One who underwrites his name to the conditions of an
   insurance policy, especially of a marine policy; an insurer.

Source : WordNet®

underwriter
     n 1: a banker who deals chiefly in underwriting new securities
          [syn: {investment banker}]
     2: an agent who sells insurance [syn: {insurance broker}, {insurance
        agent}, {general agent}]
     3: a financial institution that sells insurance [syn: {insurance
        company}, {insurance firm}, {insurer}, {insurance
        underwriter}]