Sentence:  These booze customers had until then been buying their supplies from the Sheldon , Saltis-McErlane , and Druggan-Lake gangs , and now they were competing for trade with the Torrio-Capone saloons ; once again O ' Banion 's brash recklessness had caused a <WSD>proliferation</WSD> of ill will . 
Meaning of the word marked with <WSD> tags:  growth by the rapid multiplication of parts