When describing a person as sophisticated in English, what exactly does it mean?

Depends on the context, here are all the meanings, depending on the specific situation, it can be positive or negative

sophisticated

/ s?f?st?ke?t?d; s?ˋf?st?ket?d/ adj

having or showing much worldly experience and knowledge of fashionable life (显得)世故的,老练的,高雅时髦的:a sophisticated woman 老於世故的女子* wearing sophisticated clothes 戴穿考究的衣服* sophisticated tastes sophisticated tastes.

complicated and refined; elaborate; subtle sophisticated; refined; fine; cutting-edge:sophisticated modern weapons sophisticated modern weapons * sophisticated devices used in sophisticated devices used in spacecraft ? a sophisticated discussion, argument, etc ? well thought out discussion, argument, etc.

> sophisticate / s?f?st?ke?t; s?ˋf?st?ket/ n (often ironic often as reflexive) sophisticated person 老於世故的人:The sophisticates in the office drink lemon tea; we have coffee. The sophisticates in the office drink lemon tea; we have coffee.

sophistication / s?f?st?ke?n; s?f?st?ˋke?n/ n [U] quality of being sophisticated; sophistication: proud of her newly-acquired sophistication ? the sophistication ? the sophistication of the office ? the sophistication of the office ? the sophistication of the office ? the sophistication of the office ? the sophistication of the office ? the sophistication of the office ? the sophistication of the office proud of her recently-acquired sophistication * the sophistication of modern aircraft.

When Americans say you're sophisticated it's a very positive compliment.

Pejorative: old to accidents

Positive: mature and sophisticated