spit-up noun 1spit up verb 1forms 4 noun1 •(informal) Digestive fluids and other stomach contents which are regurgitated or vomited, especially by a child.Dana Lowey Luttway anointed her son Daniel Henri "the king of spit-up" but was inspired by his daily rejections to create her first invention: the ParentSmock, a cotton bib made for parents. — 2000 spit up verb1 •To regurgitate or vomit.The baby spat up her breakfast.Don't show the dead bird to him; he'll just spit up. formsspat up · spitting up · spits up · spit-ups