振(ふ)りをするTo pretend, To act as if

ふりをする is an expression in Japanese that is used to show that someone is 'pretending to be (A)', 'putting on airs of (A)', or 'acting as if (A)'. This construction comes from a combination of the noun 振(ふ)り 'a shake', the adverbial particle を, and する. It can be thought of as meaning 'to give off the impression of (A)', or 'to shake off the impression of (A)'.

As ふり itself is a noun, this expression may be used with the attributive form of any other word.

Fun Fact

The noun 振(ふ)り has several different nuances in Japanese, with only one of them being used in this particular expression. That meaning is 'to show a certain behavior pattern on the outside'. Due to this, ふり doesn't specifically mean 'to pretend', just that what is happening on the outside may be different to what is happening within a person (either mentally or physically).