Obstreperous is one of my mum’s favourite words (I am presuming this because of the frequency with which she uses it). She often, however, uses the humorous form obstropolous which most sources list as a regional variation, but its use seems fairly widespread.
Obstreperous means noisy, difficult to control, unruly, bad-tempered or argumentative. (It is often suggested that stroppy came into usage as a slightly altered abbreviation of obstreperous.)
It was first used in the late 16th century and stems from the Latin word obstreperus ‘clamorous’ which is itself from obstrepere ‘to make a noise against’ or ‘oppose noisily’.
You can use obstreperously as an adverb and obstreperousness as a noun.
“Thou abominable obstreperous Scoundrel, why dost thou clamour at us, that do thee no wrong?”
– Plutus: or, The world’s idol. A comedy, translated by Lewis Theobald, 1715