Gelidly is an adjective that describes something that is extremely cold or icy. There are several synonyms that can be used in place of this word depending on the context of the sentence. For example, frigidly is one such synonym that suggests intense coldness. Another possible replacement is arcticly, which implies icy conditions similar to those found in the Arctic region. Alternatively, bitterly could also be used as a synonym, conveying a sense of harsh coldness. Other possibilities include frostily, wintrily, and glacially. It is important to choose the most appropriate synonym depending on the intended meaning of the sentence.