Term graph
A term graph is a representation of an expression in a formal language as a generalized graph whose vertices are terms. Term graphs are a more powerful form of representation than expression trees because they can represent common subexpressions (i.e. they can take the structure of a directed acyclic graph) as well as cyclic/recursive subexpressions (cyclic digraphs).
The phrase "term graph" is often used when discussing graph rewriting methods for transforming expressions in formal languages.