In gen., like primum, to denote the simple antecedence of an occurrence; hence, most freq. with the particles ut, ubi, quando, cum, si, etc., once , ever , at some time , at any time .

http://lila-erc.eu/data/lexicalResources/LewisShort/id/LexicalSense/n43412.4 an entity of type: LexicalSense

In gen., like primum, to denote the simple antecedence of an occurrence; hence, most freq. with the particles ut, ubi, quando, cum, si, etc., once , ever , at some time , at any time . 
In gen., like primum, to denote the simple antecedence of an occurrence; hence, most freq. with the particles ut, ubi, quando, cum, si, etc., once , ever , at some time , at any time . 

data from the linked data cloud