Learn English – What does “ad-hoc” mean

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.

When this word is used by programmers, it is a synonym for "authoritative," "standard," or "official." That's meaning number 3 in the definition you quote.

It implies that there is one best, most official, most standard way to represent the string object and this is it.

For example sometimes things can be represented using a relative link or an absolute link. Relative might be something like ../foo.txt meaning "The file foo.txt in the folder above this one" while absolute is something like \\www.example.com\fileserver\share\foo.txt which can only refer to one file on the Internet. One might say that the latter name is canonical.