Consider the abelian group $R [[\mathbb{Z}^d]]$ of all formal Laurent series over a commutative ring $R$ (a typical element has the form $\sum_{v \in \mathbb{Z}^d} \lambda_v \cdot X_1^{v_1} \dots X_d^{v_d}$ with $\lambda_v \in R$). Since there is no restriction on the coefficients, we cannot make $R [[\mathbb{Z}^d]]$ into a ring by the usual multiplication, but we get a partially defined operation in this way. It is easy to see that $R [[\mathbb{Z}^d]]$ satisfies all ring axioms, whenever all involved terms are defined. Maybe one could call such structures "partial rings".
Is there a general theory of partial (commutative) rings which abstracts from this example? I am particularly interested in the notion of ideals and quotients of them.
Thank you in advance!
Groupoids in the category theory can be described as partial groups. What you are asking for is called ringoids, see also here.