footsie

詳細解釋：

footsie 也作 foot.sy

n.Informal （名詞）【非正式用語】
The act of flirting in which one secretly touches the feet or legs of another with one`s own, as under a table.
秘密的調情動作：調情動作，其中一方在桌下偷偷地用腳或腿摩擦對方的腿或腳

<習慣用語>play footsie with
To flirt with, especially in secret.
調情：調情，尤指偷偷地
To cooperate or curry favor with in a sly or devious way.
搞秘密交易：以一種秘密的或不正當的途徑合作或搞交易
來源：
From diminutive of foot
源自 foot的小後綴