There are multiples explanations for the kanji 外す. here one of the online japanese dictionnary i am using since a long time :
https://dictionary.goo.ne.jp/word/外す/
.
1. 取り付けたり、掛けたりしていたものを取って離す。
2. 身につけていたものをとる
3. 取り逃がす。機会などを失う。逸する。roughly : lose a great opportunity : missed.
4. 一時的に、また途中である場所から退いたり離れたりする。roughly : moving something/place from a position.
5. ある集団・任務や予定などから除く。
6. 相手のものをそらして避ける。かわす : roughly : avoid something from your opponent. Dodge.
@EtenBoby i am specially talking about the 3,4 and 6. It can used for any of those definition but the meaning of Kanji is still the same. If zoro just missed then this kanji would have not been used but "見落とす " "逃す'" or even "ミスした". I think you might know this but in japanese the kanjis are used to specifically talk about something, here to describe two events which happened (one zoro missing and other one kaido dodging). So the kanji is just not miss. At least from my understanding.