Noun

1. a stick or rod used to measure the depth of a liquid. Often used to check the level at which a liquid in an invisible tank stands; gauge.

   I haven't checked the oil level of my car's motor since I lost the dipstick three months ago.

2. the penis
3. a useless person
4. (British slang) a person of inferior intellect or, more accurately, someone who makes an action that would imply this

   That referee is a right dipstick.