Antonyms for the term "filling to overflowing" could include words such as empty, depleted, drained, insufficient, inadequate, or barren. These words convey a sense of lack or insufficiency, suggesting that there is not enough of something to fill a space or meet a need. Alternatively, the opposite of "filling to overflowing" could also be expressed by words such as modest, moderate, or controlled, which suggest a more measured or restrained approach to filling or satisfying a need. These words imply a sense of balance or harmony, rather than a sense of excess or surplus.