Hmm, well, I can't find any picture, but imagine that I'm sitting to your left, and the telephone is to your right. To reach the telephone I have to incline my body towards and in front of you, either brushing into you, or causing you to have to lean backwards to avoid me. That's what "lean across" means.
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contrapositionlean across someone~ bend the upper part of your body so that it crosses in front of the person next to you
khoffIf she leaned even more, she would be falling out of whatever it is she's almost wearing.