Source : Webster's Revised Unabridged Dictionary (1913)

Swelter \Swel"ter\, v. i. [imp. & p. p. {Sweltered}; p. pr. &
   vb. n. {Sweltering}.] [From {Swelt}, v. i.]
   1. To be overcome and faint with heat; to be ready to perish
      with heat. ``Sweltered cattle.'' --Coleridge.

   2. To welter; to soak. [Obs.] --Drayton.

Swelter \Swel"ter\, v. t.
   1. To oppress with heat. --Bentley.

   2. To exude, like sweat. [R.] --Shak.

Source : WordNet®

swelter
     v 1: be uncomfortably hot
     2: suffer from intense heat; "we were sweltering at the beach"