To soliloquize is to speak your thoughts aloud while alone — or as if alone, with no real listener. It is the verb belonging to 'soliloquy', the famous kind of speech in a play (Hamlet's 'To be, or not to be'). In the theatre sense, an actor soliloquizes when the character stands on stage talking to himself so the audience can hear what is inside his head. Outside the theatre, people use it half-jokingly for anyone who talks on and on without checking whether others are listening: 'Grandpa soliloquized about the old market for twenty minutes.' That use carries a light complaint — the speech is long, private, and one-way. It is an intransitive verb, so nothing follows it directly; you soliloquize ABOUT something or ON something. The British spelling is 'soliloquise'. This is a rare, bookish word; in ordinary speech you would say 'talk to himself' or 'go on and on'.

自言自語地長篇獨白（戲劇上指「講獨白」；日常用來說某人自顧自講個沒完，帶點調侃）