[informal] grandma, [informal] granny, [informal] gran, [UK] [informal] or US regional nana, [informal] nanny [noun] [C] - the mother of a person's father or mother(formal) Would you like to sit here, Grandmother? [as form of address](saying) 'Don't teach your grandmother to suck eggs' means that you should not try to tell people who are more experienced than you something they already know.
GRANDMOTHER
Meaning of GRANDMOTHER in English
Cambridge English vocab. Кембриджский английский словарь. 2012