Quadromantic is on the Aromantic Spectrum and is characterised by only being able to experience romantic attraction inside Homestuck's troll romance system, known as quadrants.
History
Quadromantic was coined by FANDOM user Literallynotgod
Flag meaning
The red symbolises Matespritship - the flushed quadrant denoted by the <3 symbol in texting. it is the most similar to human (note: Alloromantic) romance
The pink symbolises Moiraillegience - the pale quadrant denoted by the <> symbol in texting. it is like a soulmate, your "true" partner, but with a certain social nuance. you and your moirail keep eachother happy and safe.
The grey symbolises Auspisticism - the ashen quadrant denoted by the o8< symbol in texting. they are the mediator between you and your kismesis, making sure you do not act out of turn with eachother.
The black symbolises Kismessitude - the pitch quadrant denoted by the <3< symbol in texting. this is when you feel "true hate" for someone, in a romantic way. you cannot stand eachother but yet you are attracted to eachother.
The entire zodiac is lined up in the pale strip, and inverted in the ashen to symbolise how quadrants can suddenly vacillitate and change (ie moirail to kismesis or kismesis to matesprit) this flip can either be one-sided or all of your quadrant-mates can vacilliate alongside you.