乔 is a bound form (b.f.) — it cannot stand alone as a word. You'll see it in literary or formal compounds like 乔木 (tall tree, arbor), 乔迁 (to move to a better place, often used in congratulations), and 乔装 (to disguise, literally 'tall/different dress'). Its core meaning is 'tall' or 'lofty', but it never substitutes for the everyday adjective 高.