The term 'tranquillise' is a verb meaning to make or become CALM and peaceful. The crossword solutions for this term are 'SEDATE' (6 letters), 'SOOTHE' (6 letters), 'ASSUAGE' (7 letters), 'MOLLIFY' (7 letters), 'COMPOSE' (7 letters), 'CALM' (4 letters), 'PACIFY' (6 letters), and 'APPEASE' (7 letters), and 'EASE' (4 letters). All of these words have similar meanings, which involve calming or soothing someone or something, and can be used in different contexts.