godan verb (-su), transitive verb
Rare transitive verb meaning to cause something to swell or expand. In modern Japanese, 膨らます is far more common for this meaning.
See also: 膨らます
In old documents, the expression 'to inflate a balloon' can be found.
彼はほおを膨らして不満を表した。
He puffed out his cheeks to show his dissatisfaction.