Yes, the word refund is defined in explanation to Section 54 of the CGST Act, 2017. As per the said definition, refund includes refund of tax and interest paid on:
1. Zero-rated supplies of goods or services or both; or
2. Inputs or input services used in the effecting such zero-rated supplies of goods or services or both; or
3. Supply of goods regarded as deemed exports; or
4. Refund of unutilized input tax credit at the end of any tax period in case the rate of output tax is less than the rate of input tax.
(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS: FAQ NO. 1)