Gathering and Reporting Assessments Yielding Zero Overlooked Nefarious Efforts Act This bill requires the National Intelligence Council to produce a National Intelligence Estimate (a type of intelligence community assessment) on the gray zone activities of foreign adversaries and addresses other related issues. Under this bill, a gray zone activity is an activity to advance a foreign state's interests that (1) falls between ordinary statecraft and open warfare, (2) is designed to maximize the advancement of such interests without provoking a U.S. kinetic military response, and (3) falls on a spectrum ranging from covert adversary operations to open adversary operations. The National Intelligence Estimate must analyze (1) how foreign adversaries use gray zone activities to advance interests, (2) what responses from the United States (or U.S. allies and partners) would tend to result in the escalation or de-escalation of such gray zone activities, and (3) any opportunities for the United States to minimize the extent that foreign adversaries can use such activities in furtherance of great power competition. The council must submit the estimate to Congress and make an unclassified version of key findings publicly available on the website of the Office of the Director of National Intelligence (ODNI). The council must also develop a lexicon (with definitions) of common terms for concepts associated with gray zone activities. The ODNI must publish an unclassified report containing the lexicon.