Rashi: Something that people will slander you for it, and make their mouths crooked about you. Akshus it is an expression of crooked, like "Tam Ani va'Yaksheni" (Iyov 9:20). A Mishnah (Chulin 56a) says 'its teeth are crooked and Akushos.'

R. Yonah: [It is sinful speech] - "b'Fesha Sefasayim Mokesh Ra", "Maves v'Chayim b'Yad Lashon" (12:13, 18:21). Akshus is one who does not admit to the truth.

Malbim (23-24): Even though the external deed is not evil if his conscience is straight, do not do a deed in a way that people will slander you and there will be Chilul Hashem, even if your intent is clear and acceptable.

Rashi: It is bending the lips. People should not spread their lips about you.

R. Yonah: It is saying about evil that it is good ¹ .

Malbim: Lips are more external than the mouth. Speech of the mouth is more primary. Do not do a deed that will arouse great suspicion to the point that the mouth will make your deed crooked, to say that you went in a crooked way and transgressed straightness. Distance even Lazus Sefasayim. Even if there will not be Akshus Peh to say that your deed was crooked, just there can be a little external slander. Lazus is lighter than Akshus; Luz is a small veering [from the straight]. Not only should you remove Lazus Sefasayim - also distance from it greatly, so people cannot say anything [negative] about you.