Complain Bitterly can be expressed in three different ways: RAIL (4 letters), INVEIGH (7 letters), and RAILED (6 letters). RAIL is a verb meaning to express strong criticism or protest. INVEIGH is also a verb, meaning to speak or write about something with great hostility or bitterness. RAILED is the past tense of RAIL, meaning to have expressed strong criticism or protest. All three words describe the act of complaining bitterly.