What verb should I use when somebody is saying nonsense with the purpose of making a person smile?
I was thinking of tease, but the OALD says it means, "to laugh at somebody and make jokes about them, either in a friendly way or in order to annoy or embarrass them." In my case, I am not talking of laughing at somebody or making jokes about them. I could say nonsense about something I have (presumably) done, or about something that (presumably) happened.
I would call this being silly. If my friends or I are being silly, we're usually trying to get a smile out of one another.
The words suggested in comments (play the fool,“To behave in a foolish or comical manner”, and noun buffoonery, “foolishness, silliness; the behaviour expected of a buffoon”) are good; also consider josh, “To tease someone in a kindly fashion”, and prattle, “To speak incessantly and in a childish manner; to babble”. Also see prate, near-synonyms of which include blabber, chatter, clack, gabble, gibber, maunder, palaver, piffle, prattle, twaddle.
If the "person" is a baby, one expression is "to talk baby talk." That is to speak a collection of meaningless, but good sounding syllables, because babies can't understand words anyway. But they can "smile" to pleasant sounds.
