Bodhisattva (Sk). Lit., “he, whose essence (sattva) has become intelligence (bodhi)”; those who need but one more incarnation to become perfect Buddhas, i.e., to be entitled to Nirvâna. This, as applied to Manushi (terrestrial) Buddhas. In the metaphysical sense, Bodhisattva is a title given to the sons of the celestial Dhyâni Buddhas.
Source: H.P.Blavatsky - The Theosophical Glossary