acrophobia Syllabification: (ac·ro·pho·bi·a)Pronunciation: /ˌakrəˈfōbēə/Definition of acrophobia noun extreme or irrational fear of heights. Derivatives acrophobicPronunciation: /-ˈfōbik/ adjective & noun Origin: late 19th century: from Greek akron 'summit' + -phobiaacrophobia in other Oxford dictionaries Definition of acrophobia in the British & World English dictionary