Miscellaneous items or objects; (with possessive) personal effects.

“What is all that stuff on your bedroom floor?  He didn't want his pockets to bulge so he was walking around with all his stuff in his hands.”

Unspecified things or matters.

“I had to do some stuff.”

The tangible substance that goes into the makeup of a physical object.

To fill by packing or crowding something into; to cram with something; to load to excess.

“I'm going to stuff this pillow with feathers.”

To fill a space with (something) in a compressed manner.

“He stuffed his clothes into the closet and shut the door.”

To fill with seasoning.

“She stuffed the turkey for Thanksgiving using her secret recipe.”