The phrase "am timeless" refers to a state of existence that is not bound by time or aging. Some antonyms for this phrase include "temporary," "bounded," "aging," and "fleeting." These words all suggest a limited or finite existence, in contrast to the eternal or infinite nature implied by "am timeless." Other antonyms might include "mortal," "decaying," "changing," or "impermanent." All of these words emphasize the impermanence of life and the inevitability of change, in contrast to the stability and timelessness that "am timeless" represents. Ultimately, the choice of antonyms depends on the context and intended meaning of the phrase.