兀 is a bound form (b.f.) that mainly appears in literary or formal Chinese compound words. It can mean 'high and protruding' (as in 兀立 'stand erect') or 'suddenly; abruptly' (as in 突兀 'abrupt'). Note the pinyin here is wū, which is less common than wù in modern usage, but the gloss and pronunciation given should be followed.