A formal groupoid is a groupoid whose hom-spaces have infinitesimal extension.
A formal groupoid over the point if the delooping of a formal group.
The ∞-groupoid-notion of formal groupoids is discussed at formal cohesive ∞-groupoid .
The notion of formal groupoid apparently goes back to
and
Formal groupoids in general and the de Rham space formal groupoid in particular are discussed also in section 7 of
Formal groupoids and their relation to Lie coalgebroids are discussed in section 1.4.15 of
The formal version of the notion of symplectic groupoids is discussed in