The Free On-line Dictionary of Computing (30 December 2018):

double-click

    Two clicks of a mouse button made in
   rapid succession without moving the mouse.  A double-click
   often combines the actions of selecting, and then activating
   an object in a GUI, e.g. selecting and opening a document.
   Some text editors use double-click to select the word under
   the mouse pointer.

   When used as a verb it is often written as two words with a
   space instead of a hyphen.

   (2006-07-09)