What's it mean whe a spouse is treated like a door mat?

Jonah
to be referred to as door mat to your spouse, means that you accept the way he/she treats you and say nothing, it can range from verbal abuse to physical abuse, mainly, you just accept everything that's directed at you.

There are lots more ways connected to be 'a door mat' but this is the best explaination in short that I can give you.
Hope it helps.

Is this bad thing?

Jonah
I don't know about you brother, but I would not like to be on the receiving end of any of these things.

In saying that, I have had my share of 'mental abuse' were my husband through drinking would say things just purely to annoy me, I learned over time and prayer, to walk away from it, when he started, after many mistakes on my part, praise God it has stopped now, but I would always make sure not to be up when he comes home from drinking, so not to tempt him to start again.

No Jonah it is not a nice thing to be used as a 'door mat' not at all.

Jesus did not create anyone as such a thing, we must have respect for each other, and do unto others as would have them do unto us.
Matthew 7 v 12
Therefore all things whatsoever ye would that men should do to you, do ye even so to them: for this is the law and the prophets.