As in previous beatitudes in Revelation (Revelation 1:3; Revelation 14:13), the term means happy.
The point is that the Lord God will bestow joy on the person who takes seriously what the speaker says next. That is remarkable because John’s account had become increasingly disturbing. Jesus would give comfort in the midst of horror.
15 (“Behold, I am coming like a thief! Blessed is the one who stays awake, keeping his garments on, that he may not go about naked and be seen exposed!”)