propagate

To propagate is to be fruitful and multiply, by the usual routes of reproduction, or by spreading something around like a rumor.

Condone

If you condone something, you allow it, approve of it, or at least can live with it. Some teachers condone chewing gum, and some don't.

Notarize

You usually have someone notarize your contract when you lease a car. In other words, she'll put a special, official stamp next to your signature and her own — certifying that you are in fact you.

fluctuate

Something that fluctuates varies or changes — it's the opposite of steady. Like the ups and downs of the stock market or the relationship status of a Hollywood starlet.