1
to be closed;to be blocked;to be healed (e.g. wound);to be shut up
道路は倒れた木で塞がっていた。
The road is blocked by fallen trees.
2
to be clogged;to be plugged up
あお向けに寝ると、舌やノドチンコがノドの奥に下がるため、上気道が塞がりやすくなります。
If you sleep on your back it's easier for your upper airway to be obstructed because your tongue, uvula, etc. slip towards the back of your throat.
3
to be occupied;to be taken (e.g. accommodation)
この椅子ふさがっていますか。
Is this seat taken?