One of the traditional observations about English derivational morphology is that prefixes behave differently from suffixes and are rather close to lexemes. A word-based analysis of prefixes based on this observation has been proposed, but it faces a challenge raised by the seemingly category-changing property of the comparative verb-forming prefix out-. This study aims to solve this problem in a framework that enriches the traditional generative word-based morphology with the concept of the Abstract Lexical Unit. In analyzing data, I pay attention to the degree semantics of comparative out-prefixed verbs and show that the so-called “denominal or deadjectival” out-verbs are produced as hyponyms of already existing out-verbs with sparse semantics. A pseudonym experiment demonstrates that this type of out-verb has a number/rank/action comparative interpretation, and the nouns or adjectives that occupy the head position further specify the object that is counted. The problematic type is related to its base word via head replacement rather than concatenative affixation. Drawing on these new perspective and observations, this paper shows that the traditional finding about the status of English prefixes can be maintained in a word-based approach.