Antonyms for the phrase "check thoroughly" could include "skim," "glance over," or "skimp on." These words indicate a lack of attention and detail, suggesting that the process of examination is cursory or incomplete. Other possible antonyms might include "overlook," "miss," or "neglect," implying that significant information or details are being disregarded or ignored. In contrast, synonyms for "check thoroughly" might include "scrutinize," "examine closely," or "vet," indicating a careful and thoughtful examination of all aspects of a situation or problem.