What is this electrical symbol? T with overbar in down-pointing triangle

I’d like to use an old laptop AC adapter in conjunction with an adjustable buck module as a project power supply.

It works, but I’m ignorant of some safety details; for example I’m uncertain whether my adapter, which uses a non-earthed input, is "isolated from the mains".

I’ve tried researching the symbols on the label, but one symbol which feels relevant I cannot identify:

What is that letter T in a triangle?

Does it mean "safe"?

Or "death"…?