'Opt-in,' a verb equivalent, is the act of agreeing to or asking for a given product or subscription, like a newsletter or rewards system.
OPTED - OPTEMPO - OPTH - OPTI - OPTIC - OPTINT - OPTIONALIZE - OPTIONS - OPTIR - OPTITEAM
"OPTIN." Abbreviations.com. STANDS4 LLC, 2015. Web. 28 Mar. 2015. <http://www.abbreviations.com/OPTIN>.