It's a mimetic for something "fine grained" in a positive way, with no waste of space. 내가 살던 동네 언덕에는 아담한 집들이 오목조목 들어서 있었다 In my old town on the hill, there were cozy houses laid tightly (and beautifully). similar: 오밀조밀 it's even more fine grained, emphasizing the density/efficiency at the cost of the beauty compared to 오목조목 전시장에는 주 통로를 중심으로 수많은 전시관들이 오밀조밀 배치되어 있었다. In the exhibition hall, there were numerous booths arranged tightly alongside the main aisle. related: 조목조목 word for word; clause for clause; thoroughly 대통령 비서실은 문제의 신문기사 내용을 조목조목 반박했다 The presidential secretary's office rebutted every single point of the said newspaper article.