Infirmly is a word that means weakly or unsteadily. If you're looking for synonyms, you might consider using terms like feeble, frail, delicate, shaky, or unstable. Another option could be to go with words like uncertain, hesitant, or indecisive, which convey a sense of insecurity or lack of confidence. Alternatively, you could try using adverbs like unsteadily, shakily, or weakly to describe the manner in which someone is acting or performing. Ultimately, the best synonym for infirmly will depend on the context and the specific meaning you're trying to convey, so it's important to choose your words carefully.