Real Dictionary

undercut
If your attempts to achieve something are undercut by something, that thing prevents your attempts from being effective.
verb: If you undercut someone or undercut their prices, you sell a product more cheaply than they do.

undercut in American English
a cut made below another so as to leave an overhang or concave profile
that is undercut
to make an undercut (sense 1) undercut (sense 2) in
to undercut something or someone
adjective: having or resulting from an undercut
intransitive verb: to undercut material, a competitor, a ball, etc
noun: a cut or a cutting away underneath
transitive verb: to cut under or beneath

undercut in British English
noun: the act or an instance of cutting underneath
verb: to charge less than (a competitor) in order to obtain trade

undercut in Retail
verb: When a business undercuts its competitors, it charges less than its competitors to attract customers.