In this paper we define and investigate a binary word operation that formalizes an experimentally observed outcome of DNA computations, performed to generate a small gene library and implemented using a DNA recombination technique called Cross-pairing Polymerase Chain Reaction (XPCR). The word blending between two words xwy1 and y2wz that share a non-empty overlap w, results in xwz. We study closure properties of families in the Chomsky hierarchy under word blending, language equations involving this operation, and its descriptional state complexity when applied to regular languages. Interestingly, this phenomenon has been observed independently in linguistics, under the name “blend word” or “portmanteau”, and is responsible for the creation of words in the English language such as smog (smoke + fog), labradoodle (labrador + poodle), and Brangelina (Brad + Angelina).