1
general::
Use something up so that a supply runs out or becomes insufficient, as in We ran short of envelopes, or The organization is running short of money. [Mid-1700s]
American Heritage Idioms
2
general::
Phrase(s): run short (of something)
to begin to run out of something. • We are running short of eggs. • I always keep enough so I will never run short.
McGrawhill's American Idioms And Phrasal Verbs