So firm that nothing can move it. It is used almost entirely about things inside people — faith, belief, confidence, loyalty, trust, determination, a conviction. 'She has an unshakeable belief in her son.' The picture is physical: you can push this thing, shove it, hit it with bad news and hard arguments, and it does not wobble. That is why the word carries a note of admiration, and sometimes a small note of worry too — an unshakeable belief may be strong, but it may also mean the person will not listen to any evidence. Both readings are normal, and the context tells you which. You will also see it about people themselves — 'he was unshakeable under questioning' — meaning calm and impossible to shift or rattle. Both spellings are correct: unshakeable and unshakable. The one with the e is more common in British writing and the one without is more common in American writing, and no one will mark you wrong either way in Taiwan. It is a fairly formal, written-feeling word; in speech people often just say 'nothing can change his mind'.

堅定不移的、不可動搖的（信念、信心、忠誠）