What does "feeding me slack" mean in this context?
The only time he didn't exercise was when they operated on him. When I asked him what for, the answer came at me like the thwack of a jack-in-the-box wearing a baleful smirk. "Later."
Perhaps he was out of breath and didn't want to talk too much or just wanted to concentrate on his swimming or his running. Or perhaps it was his way of spurring me to do the same-totally harmless.
But there was something at once chilling and off-putting in the sudden distance that crept between us in the most unexpected moments. It was almost as though he were doing it on purpose; **feeding me slack, and more slack,** and then yanking away any semblance of fellowship.
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This is from the book, Call my by your name, and I'm having difficulty understanding the part marked in stars. What does it mean by "feed me slack"? What's the meaning of slack here (I'm not even sure if it's a noun) or is it a phrase as a whole?