His promises had a hollow ring (=they seemed not to be sincere).
Thesaurus
THESAURUScontainer►empty
having nothing inside: Her glass was empty, so I offered her more lemonade. The gas tank is almost empty.
►hollow
used about something that has an empty space inside: Sometimes small animals make nests in a hollow tree.
►bare
used about a room or area that has very little in it: The cupboards were completely bare.
►blank
used about a computer screen, a piece of paper, or a wall that has no writing or pictures on it. You can also use blank about a CD, DVD, etc. that has nothing recorded on it: He stared at a blank sheet of paper, not sure what to write.
1 having an empty space inside: The walls are made of hollow concrete blocks. a hollow tree► see thesaurus at empty12words, events, or people that are hollow have no real worth or value, or are not sincere: hollow threats They won, but so easily it was a hollow victory. His promises had a hollow ring (=they seemed not to be sincere).3hollow eyes/cheeks etc. eyes, cheeks, etc. where the skin sinks in: prisoners of war with hollow cheeks4a sound that is hollow is low and clear like the sound made when you hit something empty: He hit the ground with a hollow thump.5someone who feels hollow feels very sad and as if nothing is important6hollow laugh/voice etc. a hollow laugh or voice is one that makes a weak sound and is without emotion [Origin: Old English holh hole, hollow place]—hollowly adverb—hollowness noun [uncountable]