Adultery in the heart is committed not only because man looks in this way at a woman who is not his wife, but precisely because he looks at a woman in this way. Even if he looked in this way at the woman who is his wife, he could likewise commit adultery in his heart.

(source)

I would have thought it would be obvious?

St. Augustine for one example, calls it that.

'He who is too ardent a lover of his wife is an adulterer.'

St. Jerome

'Those who lie together not to procreate offspring but to satisfy lust seem to be not so much spouses as fornicators.'

Gratian

'And now Lord thou knowest, that not for fleshly lust do I take my sister to wife, but only for the love of posterity, in the which thy name may be blessed for ever & Ever.'

Tobias 8:9

'You have heard that it was said to them of old, Thou shalt not commit adultery. But I say to you, that whomsoever shall see a woman to lust after her, hath already committed adultery with her in his heart.'

Matthew 5:28-29 [note it is 'a woman' without qualification]

'Well, if both parties alike are so flagitious, they are not husband and wife; and if such were their character from the beginning, they have not come together by wedlock but by debauchery. If both are not like this, I dare to say that either the wife is in a fashion the harlot of her husband or he is an adulterer with his own wife.'

St. Augustine [This is in the context of him speaking about taking drugs for sterility or abortion. It is from 'Marriage and Concupiscence']

The Gratian quote may be quoting another for his work on the canons and not direct, I don't have the primary source to look at it at the moment. Just came across it while looking for what you asked.

Happens all the time in Korea.

Lots of people there called Won.