Targum Yonasan: It is one with knowledge. Rashi - the words hint to Meshis (puts, i.e. thoughts) b'Kiros Libo (in the walls of his heart).

Radak citing Bava Basra 19b: Even a dog, which normally urinates by a wall.

Malbim: This connects with the coming words "Atzur v'Azuv." Those from Beis Yaravam will not be allowed to enter the walls (house) even of Atzur v'Azuv (one who is bound, or an Oni) in order to urinate. However, below (21:21, Melachim II, 14:26) connotes unlike this.

Rashi: Atzur is one who holds his hand (supports him), like "Zeh Ya'atzur b'Ami" (Shmuel I, 7:19). Azuv is one who has no one to hold his hand. (Neither will remain from Beis Yaravam. Also refer to 21:21:3:4 and the note there.)

Radak: Even what is abandoned and remaining, in a place that the first punishments to come on him will not cut off, I will cut it off at the end; nothing will remain.

Radak citing his father, Malbim citing Mahari: Atzur refers to money, which is Atzur (stored) in a storehouse. Azuv refers to flock, which is abandoned in the field.

Malbim: Atzur is one who is bound. Azuv is an Oni.

Rashi: Like one who eats food with his mouth, to make excrement - so I will consume after [Beis Yaravam] until they are eradicated. Radak - we find that Galal refers to excrement - "b'Gelelei Tze'as ha'Adam" (Yechezkel 4:12).

Radak citing Bava Kama 2b: Galal refers to teeth. Just like teeth consume food until it is eradicated, [so I will eradicate Beis Yaravam]. Teeth are called Galal, for they resemble marble stone called Galal - "Nidbachin Di Even Gelal" (Ezra 6:4).

Malbim: Like one eradicates matters filthy with excrement.