/ ˌdaɪləˈteɪʃn; NAmE ; ˌdɪlə-; BrE also ˌdaɪleɪ-/ noun
[ U ] ( medical ) the process of becoming wider (= of becoming dilated ), or the action of making sth become wider
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WORD ORIGIN
late Middle English : via Old French from late Latin dilatatio(n-) , from the verb dilatare spread out, from di- apart + latus wide.