To fail to succeed (at some competitive activity) by a certain margin. A noun or pronoun can be used between "lose" and "by." I can't believe we lost by just two points—a single field goal and we would have won! He lost the student election by roughly 50 votes.
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
lose by something
to be defeated by a certain amount. Our team lost by ten points. I only lost by a few points.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.