A "beaming smile" refers to a big, bright, and happy expression on someone's face, where they show joy and happiness through their smile. Full definition
Little yellow faces with beaming smiles, crying tears of joy, giving little smooches — words were not enough for my family and friends. (verilymag.com)
They had beaming smiles as they crossed the road to the Stafford Hotel, where they were expected to dine together and were later joined by Mr Murdoch's son, James, the chairman of News International. (labour-uncut.co.uk)
Walking through the 100 % PURE store threshold, we were instantly greeted by beaming smiles from two lovely store associates, Sorika and Karol. (100percentpure.com)