Meaning
A bold letter O in a square, usually red, made to label blood type O. It also serves as a capital O when spelling words with button letters.
It shows up in blood donation appeals and, playfully, in spelled-out hugs and kisses like ❌🅾️❌🅾️: “Need donors with blood type 🅾️ at the city hospital today” It is easy to mix up with ⭕ and 0️⃣, which mean a circle and the number zero.