If someone is literally running down mid and dying repeatedly, that's definitely inting. If someone has over 20 deaths, very low kills/assists, it's almost certainly inting. But, if someone is losing lane and doing poorly, at what moment do they start inting?
Lets set up a scenario. Garen top VS Fiora. Garen is getting completely rekt, he's 0/4 and the CS is 17 to 60. It's about 10 minutes into the game. He is not inting if
-he gets ganked turret dived 2v1
-he gets turret dived 1v1
-he gets flashed on and/or killed from a long range
-he gets ganked and killed before he gets under tower
-he gets inseced or stunlocked by a jungler
He is inting if
-He continues to walk up to fight fiora, knowing that it's definitely going to be death, repeatedly. (While getting 0 cs for it)
You can't tell me that repeatedly walking up to a champion you know will kill you isn't inting. You know you are going to die if this happens, and you do it anyway. That's by definition intentionally feeding/dying. If you can't recognize that you can't fight them after dying 3 times and being at a large CS disadvantage, then I am seriously questioning how you manage to get through the process of downloading league in the first place.