Other forms: showing off; showed off; shows off; shown off
When you boast or brag about something, you show off. If you insist on spelling difficult words all through dinner, even though the spelling bee is over, your little brother might accuse you of showing off.
The verb show off often has a negative connotation, so if your friend asks why you always show off, it's not a compliment. When people show off, they generally go overboard flaunting their skill or accomplishments: "It's great he won that award, but why did he have to show off about it?" Sometimes this phrase simply means "display proudly," though, like when a kid shows off their brand new roller skating skills.