fontanel
noun
fon·ta·nel ˌfän-tə-ˈnel 
ˈfän-tə-ˌnel
variants or fontanelle
: a membrane-covered opening in bone or between bones
specifically : any of the spaces closed by membranous structures between the uncompleted angles of the parietal bones and the neighboring bones of a fetal or young skull
Word History
Etymology
Middle English fontinelle a bodily hollow or pit, from Anglo-French funtainele, diminutive of funtaine fountain
First Known Use
1598, in the meaning defined above
Medical Definition
fontanel
noun
fon·ta·nel
variants or fontanelle
ˌfänt-ᵊn-ˈel, ˈfänt-ᵊn-ˌ
: a membrane-covered opening in bone or between bones
specifically : any of the spaces closed by membranous structures between the uncompleted angles of the parietal bones and the neighboring bones of a fetal or young skull