Urchin (noun)

1. A small, spiny sea creature with a round body and a hard shell.
2. A mischievous or poorly dressed child.

Origin:

From old english urchin, or old french hurchin, meaning hedgehog, or a word of unknown origin, possibly from latin hirpex, meaning harp or rake.

Examples:

1. The sea urchin is found in many different colors and sizes.
2. The sea urchin's spines are sharp and venomous.
3. The urchin's roe is considered a delicacy.
4. The urchin was a street urchin, dirty and ragged.
5. He was an urchin, always getting into trouble.