'antimonarchistic' originates from modern English formation combining the prefix 'anti-' (from Greek) and the adjective 'monarchistic', itself derived from 'monarch' + '-istic'. 'anti-' meant 'against, opposite of' in Greek.

'antimonarchistic' developed in English by attaching 'anti-' to 'monarchistic' (from 'monarch' < Late Latin/Old French < Greek 'monarkhos' 'single ruler'), producing the modern adjective meaning 'opposed to monarchy'.

Initially the elements meant 'against' + 'rule by a single ruler', and over time the composite has been used to mean more broadly 'opposed to monarchy or monarchism' in political contexts.