The term "illdefined" refers to something that is unclear, ambiguous, and lacks definition. Antonyms for "illdefined" include words like precise, clear, specific, and distinct. Precise refers to something that is exact and accurate, leaving no room for confusion. Clear indicates that something is easy to understand and free from ambiguity. Specific implies that something is detailed and well-defined, leaving no room for doubt. Distinct refers to something that is easily recognizable and distinguished from others. In short, using the antonyms of "illdefined" can help to communicate ideas and concepts more clearly and precisely.