Source : Webster's Revised Unabridged Dictionary (1913)

Tense \Tense\, a. [L. tensus, p. p. of tendere to stretch. See
   {Tend} to move, and cf. {Toise}.]
   Stretched tightly; strained to stiffness; rigid; not lax; as,
   a tense fiber.

         The temples were sunk, her forehead was tense, and a
         fatal paleness was upon her.             --Goldsmith.
   -- {Tense"ly}, adv. -- {Tense"ness}, n.

Source : WordNet®

tensely
     adv : in a tense manner; "he sat down tensely"