Gilet vs Vest: What Exactly Is A Gilet?

I was browsing through different clothing brands' websites when I saw a photo of what I would call 'sleeveless biker leather jacket' listed as biker gilet.

Source: Biker Gilet by MANGO

My instant reaction was, "Um...what's a 'gilet'?"
The image of my husband shaving his 5 o'clock shadow in front of the mirror using his Gillette razor came floating into mind but I immediately shook off the thought, because the picture above from Mango's website is telling me otherwise.

OK, so I've come to terms with the fact that gilet is a piece of clothing—but what is it exactly? I put on my research hat (translation: my imaginary Googling hat) and got to work...

Back in August, Vogue.com made gilet their Fashion Word of the Day (if the people from Vogue thought of Gillette, I'd say it's perfectly acceptable that I did, too).
According to Vogue, gilet is simply a French synonym for vest. It is also old-school, and I mean super old-school; it dates back to the 19th century when both women and men wore it as waistcoat.

eBay has a more in-depth article on gilet where you'll find out that gilet isn't only meant for scoring sartorial points, but is worn for practical purposes as well. Hunters, hikers and cyclists are known to wear them when they're out and about.
And guess what? Most of us have donned a gilet, too, most probably during the cold days of winter. When I lived in New Zealand, walking to classes in my sleeveless padded jacket (to show off the cute sleeves of my top underneath, of course), I had no idea I was wearing a gilet.

Some people might scoff and say "Should we maybe stop with this snooty nonsense and let's call it what it is: a vest". I think there will always be debates on when to call that sleeveless thing a gilet and when to call it a vest—or even when to simply call it a "sleeveless something".

Mango, on the other hand, seems to name almost everything sleeveless they're selling as gilet (note: if the link doesn't take you straight to the gilet page, search for the term on their website):

Source, all from Mango website

So you can see why this can be confusing to some people—or is it just yours truly who is confused? Because I would have called the top in the top-right photo something like sleeveless boyfriend blazer, while the bottom left one is sleeveless denim jacket to me. The other two would simply be sleeveless kimono top and sleeveless padded vest.

Hmmm. Calling a sleeveless top "sleeveless" just isn't as chic as calling it gilet, isn't it? Especially when you say the term in your best French accent.

This topic is still a head-scratcher for me. Is it OK to call any sleeveless outerwear as gilet, then? I might have to start going around and mentioning "gilet" whenever I spot something in a store that could pass as one; if the reaction from the sales assistant (and anyone else who heard it) is positive, I'd definitely consider stamping the term permanently in my fashion dictionary.

Is this not a "sleeveless denim jacket", but a denim gilet?

I have a strong feeling, though, that people are going to think I'm crazy for repeating the name of a famous razor and shaver brand when I'm pointing at that sleeveless thing...

Extra tip: Gilet is pronounced as "jhee-lay", and not "gee-lay"—gotta French it up, peeps.