so ‧ lid ‧ i ‧ ty /səˈlɪdəti, səˈlɪdɪti/ BrE AmE noun [uncountable]
[ Word Family: noun : ↑ solid , ↑ solidarity , ↑ solidity , solids, ↑ solidification ; verb : ↑ solidify ; adverb : ↑ solidly ; adjective : ↑ solid ]
1 . the strength or hardness of something:
the solidity of the stone walls
2 . the quality of something that is permanent and can be depended on:
the solidity of middle-class institutions