Matchless means so good that nothing else can stand beside it — without a match, without an equal. A matchless voice, matchless courage: the word glows a little. You will not hear it much in the street; people now say unmatched, unbeatable, or one of a kind. Though actually the tidy gloss “very good” is a bit too small. It is not only praise; it says there is no equal. It is built from match (an equal) plus -less (without). An older English word make once meant “equal / companion,” and Middle English makeless already meant “having no equal”; matchless continues that idea. It is a rather bookish, even old-fashioned adjective, kind in tone, not cold.