Relating to, characterized by, or causing loud, excessive, or unrestrained laughter.
From Latin 'cachinnus' (loud laughter) with the adjective suffix '-atory' (relating to or tending toward). The suffix typically indicates something that tends to produce or promote the quality described by the root. This is an extremely rare word in modern English.
This adjective is so archaic that it's practically archaeological—if something were 'cachinnatory,' it would be something that makes people laugh uncontrollably, but you'd never actually hear anyone use this word today!
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