[…What is ice?]
When Harloys was my teacher, her questions were always designed to stimulate my mind. In a similar fashion, my System started off by giving me a question and telling me to think about it by myself.
But unlike my confused self from back in the day, I could now count myself as an ice magic grandmaster.
"Ice is a special form of water. Ice magic is a branch magic of water magic. As long as I pay a certain amount of mana, I'll be able to quickly change the form of water I create into ice."
That was Roland Blackhand's answer to this question back in my second life. It was a transmigrator-like answer, very scientific and practical, and was how he had developed his Ice Hallucination technique which was most suited to his combat style.