Section 2(1)(66) of the Companies Act, 2017 defines the term as under:

(66) “special resolution” means a resolution which has been passed by a majority of not less than three-fourths of such members of the company entitled to vote as are present in person or by proxy or vote through postal ballot at a general meeting of which not less than twenty-one days’ notice specifying the intention to propose the resolution as a special resolution has been duly given:

Provided that if all the members entitled to attend and vote at any such meeting so agree, a resolution may be proposed and passed as a special resolution at a meeting of which less than twenty-one days’ notice has been given;