There is no universally accepted term. How you describe such a thing depends on context.
For instance, in second language acquisition people differentiate between error and mistake the first being a sign of a systematic lack of competence in a particular area whereas the latter is just an accident that does not signify anything about the speaker's ability to produce a given form.
In other contexts, people talk about slips of the tongue to indicate the accidental nature of these incidents. (This would probably describe your example). However, it turns out that these 'slips' can be quite systematic among native speakers, particularly when it comes to agreement and tense. Some terms to describe these things include zeugma or anakoluthon (although the latter is not used in English).
Mistakes/slips also often occur where there are similar expressions that get blended in the speaker's/hearer's mind. There's a whole traditional classification of such misspoken expressions that includes terms like malapropism, spooonersim, eggcorn, mondegreen, or the recently coined crash blossom. All of these have detailed Wikipedia entries if you want to find out more.