From Longman Dictionary of Contemporary Englishsaddosad‧do /ˈsædəʊ $ -oʊ/ noun (plural saddos) [countable] informal someone who you do not respect, especially because you think their interests are boring or strange a bunch of saddos dressed up as science fiction characters
Examples from the Corpus
saddo• It's a fantastic life, in which the message is clear: Don't be a saddo. 