An archaic adverb is a word or phrase that is no longer commonly used in modern language. The crossword solutions for this term are ERST (4 letters), EER (3 letters), EEN (3 letters), and ALEE (4 letters). ERST is an archaic adverb meaning 'FORMERLY' or 'at first'. EER is an archaic adverb meaning 'EARLY'. EEN is an archaic adverb meaning 'ONCE'. Finally, ALEE is an archaic adverb meaning 'on the lee side', which is the side of a ship or object away from the wind.