From Longman Dictionary of Contemporary Englishpipsqueakpip‧squeak /ˈpɪpskwiːk/ noun [countable] old-fashioned UNIMPORTANTsomeone that you think is not worth respecting or paying attention to, especially because they are small or young
Examples from the Corpus
pipsqueak• If a pipsqueak mob like the Green Party can do it, why can't the mighty Labour Party?• Fernandez is a pipsqueak compared to other drug dealers.• I was damned if some nineteen-year-old pipsqueak with zits and a clip-on tie was going to make me feel loathsome. 