What this mean on Facebook messenger?

[Anonymous]

The person is unavailable on messenger does that mean they block me or they deactivated their account?

[kespethdude]

Here's how to find out, but you need either the actual Facebook app (NOT Messenger), or a web browser, and go to Facebook as an unregistered user (i,. e. NOT logged in) and try to view that user's account. If it's visible in this case, s/he blocked you. If not, the account is not currently active. Another way to find out is to ask a mutual friend if they can see the account of the user in question. Both of thee are forms of the "down for everyone or just me" method (yes, I AM basing this on that website as it is basically the same idea), and is the easiest way to tell if another account is inaccessible only to you (blocked) or to all (inactive).

[Anonymous]

they deactivated the account or blocked you on the messenger

[Wise4myage]

According to Google, it can mean either thing.