Unusually is a synonym of abnormally.

As adverbs the difference between unusually and abnormally

is that unusually is in an unusual manner while abnormally is in an abnormal manner; in a way that deviates from a standard, norm, or average {{defdate|first attested in the mid 19^th cnetury}}{{reference-book | last =| first = | authorlink = | coauthors = | editor =brown, lesley | others = | title = the shorter oxford english dictionary | origdate = | origyear = 1933| origmonth = | url = | format = | accessdate = | accessyear = | accessmonth = | edition = 5th | date = | year =2003| month = | publisher =oxford university press | location =oxford, uk | language = | id = | doi = | isbn =978-0-19-860575-7 | lccn = | ol = | pages =6| chapter = | chapterurl = | quote =}}.