so-and-so - Definition from Longman English Dictionary Online

so-and-so
noun

so-and-so plural so-and-so's

1 [uncountable] used to refer to a particular person or thing when you do not give a specific name [↪ such and such]:

I'd find myself thinking, 'I wonder what so-and-so is doing?'

2 [countable] a very unpleasant or unreasonable person - used when you want to avoid using a swear word:

Peter can be a real so-and-so at times.

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.

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so-and-so noun

so-called adjective