To laugh quietly. (Cambridge Dictionary)
To laugh inwardly or quietly. (Merriam – Webster)
To make a continuous gentle sound resembling suppressed mirth. (Merriam – Webster)
Laugh quietly or inwardly. (Oxford Dictionaries)
When you chuckle, you laugh quietly. (Collins Dictionary)
Why We All Need A Good Chuckle: A Laughter Expert’s Advice.
What is the difference between chuckle and laugh?