To suffocate is first of all about air: to die, or almost die, because you cannot breathe. A person can suffocate under a pile of sand; a fire can be suffocated when you cover it and take its air away. This sense is used both ways — 'he suffocated' (it happened to him) and 'the smoke suffocated him' (it did it to him).

But this entry is about the feeling, and the feeling is the more common use in everyday talk. When you say you feel suffocated, usually nothing is wrong with the air at all. You mean you feel trapped — no space to move, no space to choose, someone always watching you. A student can feel suffocated by parents who ask about every hour of the day. A worker can feel suffocated by a boss who checks every email. A person can feel suffocated in a relationship where the other person wants to be together all the time. The word is strong and it is emotional; it says the pressure is so close around you that it is hard to live normally.

Notice the shape it usually takes: 'I feel suffocated', 'I felt suffocated by...'. It is nearly always passive — something is doing it to you. Also notice that the person doing the suffocating is often not cruel. Parents who suffocate their child usually love the child very much. That is part of why the word is useful: it describes love or care that has become too heavy. 'Suffocating' as an adjective works the same way — a suffocating marriage, a suffocating small town, suffocating heat (here the heat is real, but you are still describing how it feels to be inside it, not real danger).