Reborrowing is the process where a word travels from one language to another and then back to the originating language in a different form or with a different meaning. This path is indicated by A→B→A, where A is the originating language, and can take many forms.

The result is generally a doublet, where the reborrowed word exists alongside the original word, though in other cases the original word may have died out. Alternatively, a specific sense of a borrowed word can be reborrowed as a semantic loan; for example, English pioneer was borrowed from Middle French in the sense of "digger, foot soldier, pedestrian", then acquired the sense of "early colonist, innovator" in English, which was reborrowed into French. In other cases the term may be calqued (loan translated) at some stage, such as English ready-to-wear → French prêt-à-porter (1951) → English prêt-à-porter (1957).

In some cases the borrowing process can be more complicated and the words might move through different languages before coming back to the originating language. The single move from one language to the other is called "loan" (see loanword). Reborrowing is the result of more than one loan, when the final recipient language is the same as the originating one.