Headlong rhymes with:
budlong, budlong, chamlong, daylong, furlong, hourlong, monthlong, weeklong, birdsong, budlong, chamlong, daylong, furlong, headstrong, hissong, hourlong, hussong, hysong, monthlong, plainsong, scuppernong, ssangyong, weeklong
Headlong sounds like:
headlines, headlining, hoodlums, hotaling, hotaling's, hotlines, huddling