Source : Webster's Revised Unabridged Dictionary (1913)

Insurer \In*sur"er\, n.
   One who, or that which, insures; the person or company that
   contracts to indemnify losses for a premium; an underwriter.

Source : WordNet®

insurer
     n : a financial institution that sells insurance [syn: {insurance
         company}, {insurance firm}, {insurance underwriter}, {underwriter}]