The 27-year-old last played for Finnish club Inter Turku, where he scored 16 times in 23 appearances.
Gnabouyou played five times for Marseille from 2008-10, replacing Mathieu Valbuena on his Ligue 1 debut against Le Mans (and incidentally in his last too, against Valenciennes in 2010).
The Frenchman has been trialling with the Devon-based club since his retirement, and netted twice for them in a recent friendly.
After impressing in training, Torquay have offered him a contract until January.
"We've not agreed terms so there's still quite a bit of work to do, but it's something that's ongoing," manager Gary Owers told BBC Sport.
"He's mobile, he's athletic, he's quick and, looking at his stuff – which I did do before I invited him over – he looks like he can finish if he gets a chance."
Torquay are currently 23rd in the National League, and desperately in need of a goalscorer to get them up the table.
Naturally, Owers is hopeful that Gnabouyou joins.
"He is someone who is attracting a lot of attention... someone who's scored lots of goals in the last couple of seasons," noted the Gulls chief.
Gnabouyou will be glad to hear that Plainmoor is just like the Stade Velodrome. Honest.
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