counterword

counter- +‎ word

counterword (plural counterwords)

1. A word (for example so) that is frequently used in a reflex-like manner in an answer and that has thereby quickly taken on a new, much less specific or much looser meaning or is even almost meaningless and performs a completely new function.
2. Such a word (or a word that has gone through a similar change) when not used as a reflex-like answer.

Since such change occurs much more rapidly than the change in meaning all words go through, and since such words are even sometimes still simultaneously used in their original sense, the new usage is often considered incorrect by some speakers. Other examples include nice, terrific, terrible, awful, tremendous, and swell.