The word "under taken" implies action or undertaking a task, project, or responsibility. Antonyms for this phrase can be "abandoned," "ignored," "neglected," or "forgotten." These words express the opposite of taking action or responsibility. Abandoned means leaving something behind or giving up. Ignored means not paying attention or disregarding. Neglected means failing to take care of something or someone. Forgotten means not being remembered or given attention. It is important to understand different antonyms for words to be able to use them effectively in communication and writing. Antonyms provide a range of vocabulary to convey different meanings and nuances.