Two related uses. (1) As a noun, 'insincerity / false intent', most often in the four-character set
虚情假意 (xūqíng-jiǎyì, 'fake feelings, false intent'). (2) Adverbially,
假意 + verb = 'to pretend to V', e.g.
假意答应 'pretended to agree',
假意关心 'feigned concern'. The opposite is
真心 (zhēnxīn, sincerity).
