Someone that will always help you get rid of that boner.

A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

“Accidentally” stuck

sis are parents are home we should stop

you ok meet me inside the shower

sis ok see you there

stepsister means someone who gets stuck in a washing machine

The person who is always complaining about how you took her room when you moved in

Step sister is always stuck in the Washing mashine at the right time to get rid of yout Boner.