Noun
(figuratively, by extension) An impediment that prohibits the use, adoption, application, etc. of (something).
The class has a number of prerequisites, so sadly there is a barrier to entry.
(finance) A cost that must be incurred by a new entrant into a market, but which does not apply to incumbents.
Used other than figuratively or idiomatically: see barrier, to, entry.
Source: en.wiktionary.org