[karma_vaccum123]

Anyone can call themselves a unicorn

[verandaguy]

I thought it was specifically a word for new-ish companies with a $1B+ market cap that hadn't been bought by a larger, older company.

[ceejayoz]

$1B is easy.

https://signalvnoise.com/posts/1941-press-release-37signals-...

[idlewords]

The term is defined in the first sentence of the linked article.