Shulchan Aruch Even HaEzer 119.4 said that there's is a Mitzva to divorce one's bad wife.
אִשָּׁה רָעָה (ה) בְּדֵעוֹתֶיהָ, וְשֶׁאֵינָהּ צְנוּעָה כִּבְנוֹת יִשְׂרָאֵל הַכְּשֵׁרוֹת, מִצְוָה לְגָרְשָׁהּ:
A wife who has a bad temper (Baer Heytev (paraphrasing Yevamot 63b: One who prepares for him the tray and turns her back upon him.) and which is not modest as Yisrael girls, and who is quarrelsome, it is a mitsva to divorce even if she is the first wife
What is considered a bad wife?
Bais Shmuel there said:
היינו מקשטא ליה תכא ומהדרא ליה גבה שהיא בעלת מריבה מצוה לגרשה...
Which I do not know what does it mean?
What I found is Yevamos 63b: "One who prepares for him (Her husband) the tray and turns her back upon him (Euphemism)."
But I do not understand it. How is the "Euphemism" understood?