The word "concretize" refers to giving a definite form or shape to an idea or concept. Antonyms for concretize could include abstract, vague, indefinite, ambiguous, unclear, or obscure. Abstract refers to ideas or concepts that are not tangible or specific, while vague suggests a lack of clarity or precision. Indefinite implies that something is not clearly defined or specified. Ambiguous means a lack of clarity or uncertainty, while unclear suggests a lack of visibility or definition. Lastly, obscure implies something that is not easily understood or known. By learning these antonyms for concretize, one can better understand the range of possibilities for describing abstract concepts.