What does "pneumatic" mean when applied to a person?

For example, in this review of the movie Unknown, Mark Kermode refers to Liam Neeson's character's wife as being played by "X-Men's pneumatic January Jones".

I'm never quite sure whether this refers to her attitude, her physique, a particular aspect of her physique, or something else. I don't think I've ever seen the word used to describe a man. Any suggestions?

When a female is described as pneumatic it means she has large breasts (possibly artificially augmented by plastic surgery).

To my mind, there's also the implication of her being both well-equipped and possibly available for bouncy bouncy / mattress dancing (slang euphemisms for sexual intercourse).

Per @z7sg's answer and @Jimi Oke's comment, Aldous Huxley particularly favoured the word, using it no less than 15 times in Brave New World! (less than half have any sexual connotation though - the majority are pneumatic chairs/sofas/shoes/etc.) Huxley's usage, which strikes me as somewhat bizarre, seems only loosely related to the standard meaning today.

The modern (sexist, to my ear) usage may have started with T.S. Eliot's Uncorseted, her friendly bust / Gives promise of pneumatic bliss (Whispers of Immortality, 1920). Over a hundred years earlier, and still sometimes today, the pneumatic body has been used to mean spiritual body which would be resurrected (as opposed to corporeal body which decays after death - see 1 Cor. 15:44).

I've never heard the term applied to a man, but if I did come across it, I wouldn't infer any sexual or spiritual conotations - I'd just assume it meant someone who looked a bit like the Michelin Man.

There is a precedent for the usage of the word pneumatic to describe the desirable female character Lenina Crowne in Aldous Huxley's Brave New World.

"Lenina Crowne?" said Henry Foster, echoing the Assistant Predestinator's question as he zipped up his trousers. "Oh, she's a splendid girl. Wonderfully pneumatic. I'm surprised you haven't had her."

In describing Lenina, pneumatic means well-rounded, curvy, and bouncy, in the sexual sense of the word.

"Every one says I'm awfully pneumatic," said Lenina reflectively, patting her own legs.

Before this it was used by T.S. Eliot in the poem Whispers of Immortality, conveying the sensual pleasure of a woman's bosom.

Grishkin is nice: her
Russian eye is underlined for emphasis;
Uncorseted, her friendly bust
Gives promise of pneumatic bliss.