Pronounced: xīn yǎn
Literally: heart/mind eye; eyes of the mind
Means: calculating, wily
The post “Dumb Americans”and one of its comments explain it this way:
“To many Chinese, Americans don’t have xin-yan (心眼, meaning, literally, eyes of the mind; or figuratively, calculating, wily), they trust what you say, and they believe you are doing what you say you are doing. For that, they are dumb. …to speak your mind straightforwardly, to defend your position forcefully, and to uphold what you believe without compromise, are all signs of childishness. A lot of Americans, alas, fill that bill.” [Link 1]
“There is another xinyan word/phrase: 实心眼。 It means solid, blocked 心眼 (note that 眼 also means “hole”), and, figuratively, honest, lack of wily flexibility. It is sort of like 没心眼，the difference being, 没心眼 means no 心眼 at all while 实心眼 means not necessarily the absence of of 心眼，but the insistence on doing things in a more principled way. It is generally recognized that, in China, 实心眼吃亏 — if you are too principled, you stand to lose, you suffer, and you are dumb.
“I read somewhere that the Eskimos have a lot of words for snow; and heck, we Chinese have tons of words for 心眼!” [Link 2]