When you chat at length about something without really knowing much about it, you smatter. If you smatter about sea creatures, it would be wise not to do it in front of a marine biologist.
You're probably more familiar with the word smattering, which describes a little bit of something. The verb smatter is much less common, even nearly obsolete. In addition to "talk foolishly about something," it can also mean "dabble in or play around with," the way you might smatter in playing the guitar, not taking it very seriously. Smatter comes from Scots dialect, and is still commonly used in Scotland.