The Jargon File (version 4.4.7, 29 Dec 2003):

stubroutine
 /stuhb'roo?teen/, n.

    [contraction of stub subroutine] Tiny, often vacuous placeholder for a
    subroutine that is to be written or fleshed out later.


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

stubroutine

   /stuhb'roo-teen/ [contraction of "stub subroutine"] Tiny,
   often vacuous placeholder for a subroutine that is to be
   written or fleshed out later.

   [Jargon File]