snigger

“Here the unfeeling Toad broke into a snigger, and then pulled himself together and tried to look particularly solemn.”

“[…]presently the Mole's spirits revived again, and he was even able to give some straight back-talk to a couple of moorhens who were sniggering to each other about his bedraggled appearance.”

“Peter, after the manner of man at the breakfast table, had allowed half his kedgeree to get cold and was sniggering over a letter. Sophia looked at him sharply. The only letter she had received was from her mother. Sophia's mother was not a humourist.”