noun one who, or that which, fosters.
2. foster ·noun a forester.
3. foster ·vi to be nourished or trained up together.
4. foster ·vt to feed; to nourish; to support; to bring up.
5. foster ·vt to cherish; to promote the growth of; to encourage; to sustain and promote; as, to foster genius.
6. foster ·vt relating to nourishment; affording, receiving, or sharing nourishment or nurture;
applied to father, mother, child, brother, ·etc., to indicate that the person so called stands in the relation of parent, child, brother, ·etc., as regards sustenance and nurture, but not by tie of blood.