oov

An item in a television (especially news) broadcast consisting of pictures alone, to be played on screen while the presenter continues to talk out of vision and provide commentary.

Initialism of out of vocabulary: describing a term encountered in the input which is not present in a system's dictionary or database of known terms.

Rather, the n-grams are calculated as usual only for the most common k words, and all other words are regarded as Out-Of-Vocabulary (OOV) items and mapped to a single token such as .