hairpin trigger 

Really called a hair trigger. It's a modification made to a gun which makes it respond to very little pressure on the trigger. Allows for faster firing.

If you get a semi-auto chopper, you better put a hairpin trigger on it.

hairpin trigger by Correy April 12, 2007

Hairpin Headache 

The soreness that results from wearing a hairstyle for a long period of time that pulls at the roots of the hair.

Alice took down my hair from its style, saving me from a hairpin headache later on.

Hairpin Headache by LeShea Setsuna October 11, 2008

hairpin scrollbar 

A hairpin scrollbar is an object used to scroll down a webpage that is impractically too small due to the large amount of content, often unnecessary, on said webpage.

Man, I hate these top ten articles that take me to pages with a hairpin scrollbar. I ain't readin' all this mess, I need bullet points.

hairpin scrollbar by jona777than September 8, 2013

Among us hairline 

Only the most elite members of society are seen with these. It is a privilege, but also a massive responsibility to have an among us hairline. The among us hairline is a symbol of leadership and superiority, which is why you have never seen one, for holders of the among us hairline do not show themselves amongst average human beings.

Bro got that among us hairline, damn.

Among us hairline by ChardNard420 September 24, 2021

Harping 

To rag on. To make fun of. To get on someones case.

Joe "Billy you are an idiot I cant believe you did that"
Billy " Quit harping on me man"

Harping by jbabz October 7, 2009

dropping hairpins 

To give hints that one is gay. Usually in the act of determining whether or not a person is safe to come out to. Also to see if an object of desire is also gay.

When I was talking with Jim, I dropped a couple hairpins, but I don't think he picked up on them.

dropping hairpins by eggie December 2, 2003

Fucked Up Hairline 

When your hairline looks awful or ghastly.
This may even cause others who see it to have a nauseating effect due to witnessing such an atrocity.

Drew aka Drewbacca perfectly exemplifies this definition:
His hairline resembles a staircase, now this wasn't done on purpose hence the "Fucked Up Hairline"

Visual Evidence:
Exhibit A:
http://farm4.static.flickr.com/3485/3183251697_f95103f461.jpg
Exhibit B:
http://farm4.static.flickr.com/3128/3178603647_11c3f91e80.jpg

Fucked Up Hairline by Hypebeast2009 January 10, 2009