The inverted black triangle was an identification badge used in Nazi concentration camps to mark prisoners designated asozial ("asocial")[1][2] and arbeitsscheu ("work-shy"). The Roma and Sinti people were considered asocial and tagged with the black triangle.[3][1] The designation also included alcoholics, homeless, beggars, nomads, prostitutes, murderers, thieves, and violators of laws prohibiting sexual relations between Aryans and Jews.[1][2] Women also deemed to be anti-social included nonconformists and lesbians.[4][2] The term "asocial" was also originally applied to heterosexual women who engaged in sex outside of marriage.[citation needed]

https://en.wikipedia.org/wiki/Black_triangle_(badge)

Disambiguation: https://en.wikipedia.org/wiki/Black_triangle

Angularis nigra, Latin for 'black angle', also known as open gingival embrasures, and colloquially known as "black triangle", is the space or gap seen at the cervical embrasure, below the contact point of some teeth.

https://en.wikipedia.org/wiki/Angularis_nigra

A black triangle appearing after the trade name of a British medicine (or vaccine) indicates that the medication is new to the market, or that an existing medicine (or vaccine) is being used for a new reason or by a new route of administration.[1][2][3]

Examples of how it might appear:

NewDrugTradeName▼

NewDrugTradeName▼

The black triangle also highlights the need for surveillance of any Adverse Drug Reactions (ADRs) that might arise from the use of a new medication. The Medicines and Healthcare products Regulatory Agency (MHRA) encourage anyone to voluntarily report ADRs (however minor) via the Yellow Card Scheme to gather more information and gain more understanding of a new medication.

After a new medicine (or vaccine) has been brought to the market there is still a lot that can be learned about the drug from its widespread use. Similarly, if an existing drug is being used in a situation where it was not used before or if it is being given by a different route of administration much can still be learned about its new or modified use.

The black triangle label generally stays with the new drug (or new use of an existing drug) for at least 5 years, when it is reviewed, and after this time the black triangle label may or may not be discontinued.

https://en.wikipedia.org/wiki/Black_triangle_(pharmacovigilance)

Storm Nickname "the black triangle": https://en.wikipedia.org/wiki/January_1998_North_American_ice_storm

https://en.wikipedia.org/wiki/Black_triangle_(UFO)

The Black Triangle and HecateBut the black triangle has an even older orgin and in ancient times was used in the occult to represent the three aspects of the demoness Hecate known as the maiden, the mother and the crone, en entity held in high regard by Wiccans and Satanists alike:

https://messianicevangelicals.wordpress.com/2020/03/18/vision-of-the-united-states-hecates-curse-of-the-black-triangle/

https://discover.hubpages.com/relationships/Lesbian-Symbol-Black-Triangle

These last 2 links are a fucking treasure trove!