Squared Saltire

From Japanese digital TV, as a “closed entry” traffic sign.

Japan's broadcasting standards body, ARIB (Association of Radio Industries and Businesses), defined a set of symbols that digital TV can show in on-screen text, including many road and traffic signs for traffic information. When Unicode took that set in, ⛝ came along as ARIB sign 9027, “closed entry”. Its neighbour ⛜ is sign 9026, the version for a closed entry on the left.

The name explains the drawing. A saltire is the heraldic word for a diagonal cross, the one known as St Andrew's cross and seen in white on blue on Scotland's flag. “Squared” means the cross sits inside a square.

Someone sent me ⛝ — what do they mean?

Read it as a boxed X: closed, blocked, crossed out or no.

Few people who type ⛝ know its Japanese TV origin, so the picture carries the meaning. In a list it can mark something as cancelled or unavailable; on a map or diagram it can mark a closed way in. If it looks like a ticked checkbox to you, the sender may have meant one, though the usual checkbox character is ☒.

If you see an empty rectangle instead, your font simply doesn't include this symbol; the sender saw a boxed X.