what ‧ cha ‧ ma ‧ call ‧ it /ˈwɒtʃəməˌkɔːlɪt $ ˈwɑːtʃəməˌkɒːl-, ˈwʌtʃ-/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: what you may call it ]
spoken a word you use when you cannot remember the name of something:
I’ve broken the whatchamacallit on my bag.