foster /ˈfɒstə/adjective 3verb 4noun 3forms 5phrases 1 adjective3 •caring for a child as a mother or father would, though the child was born into another familyfoster parents •Receiving such care. •Related by such care.We are a foster family. verb4 •To nurture or bring up offspring, or to provide similar parental care to an unrelated child.Some say that Rauens foster forlorne children, / The whilst their owne birds famish in their nests: / Oh be to me though thy hard hart say no, / Nothing so kinde but something pittiful. — 1588 •To promote the development of something; to cultivate and grow a thing.Our company fosters an appreciation for the arts. •To nurse or cherish something. •(no longer used) To be nurtured or trained up together.There Florimell, in her first ages flowre, And passing beautie did eftsoones reveale, Was fostered by those Graces — 1596 noun3 •The care given to another; guardianship. •(informal) A foster parent.Some fosters end up adopting. •(no longer used) A forester.A griesly Foster forth did rush. — 1590 formsfostered · fostering · fostereth · fosters · fosterest Phrases with foster foster upTo raise up (something); to foster, nurse, increase or strengthen (something).