1 [no object] : to become larger than normal

• Her broken ankle swelled badly.

— often + up

• The bee sting made my whole arm swell up.

2 [+ object] : to make (something, such as a river) larger or more full than normal

• Heavy rains swelled the river.

3 : to increase in size or number

[no object]

• The population has swelled/swollen in recent years.
• The economy is swelling at an annual rate of five percent.

[+ object]

• Immigrants have swelled the population.

4 [no object] : to become louder

• The music swelled.

5 : to cause (something, such as a sail) to stretch outward and become full

[+ object]

• The breeze swelled(out) the sails.

[no object]

• The sails swelled(out) in the breeze.

6 [no object] : to feel an emotion strongly — + with

• His heart swelled with pride.