What is a lagger?

I was wondering what the actual definition of a lagger is. I searched it and found very different results... Here are some of the definitions I found

• person who lags
• one who installs lagging (I'm assuming this is illegal)
• someone who is lazy (so by interpretation someone who doesn't try until the end on purpose?

Anyways here's the live bullet game in which I encountered the word (here if you just want to look at times/no analysis

https://www.chess.com/live/game/2550030256

now he could have said "flagger" but let's be honest... 10 moves before the game finished I was down by 6 seconds. If I was a person who flags, my true goal would be making sure my opponent loses on time before I get checkmated, but the issue in this argument is that we were even on time by move 35 in which I was totally winning. So can someone explain why my opponent said "lagger"?

EDIT: As I was going through a replay of the game (for a slower analysis) I realized I missed a bunch of tactics in the analysis so please forgive me, my mind was still in bullet mode.