“At full tilt” means flat out, at top speed, as fast as possible. Its origins don’t have anything to do with being unsteady, at an angle, or, indeed poker.
The term derives from the sport of jousting, or tilting (ever heard of ’tilting at windmills’?), and ‘at full tilt’ is believed to have first come into use as an expression in the mid-1600s. Common theories (check out etymonline.com for even more good stuff) are that it comes from either the practice of leaning in to meet the attack when jousting, or, conversely, from tilt or tent, referring to the flimsy barrier that separates the two riders when they joust.
Examples of ‘at full tilt’
I ran down the hill at full tilt.
We’re going to need to work at full tilt to get this done in time.
Is it still in common use? Depends who you ask. I’m a Millennial, and I use it; my parents’ generation certainly did. On the whole, it’s probably more likely to be used in British English than American English.
It’s one of those phrases you can use to hint at a character’s background in contemporary work such as a thriller – maybe your anti-hero is British and gives himself away with it, for example.
If you’re writing fantasy or sci-fi, you can also adapt this type of expression. If (random example, honest) your invented culture includes people swinging on big metal balls hung from cranes, you’d use ‘at full swing’. (Oddly enough, ‘in full swing’ is another weird English idiom that I probably will be covering on another day.)
What is etymology, and why are you excavating it?
Etymology is like the archeology of a language (definition: the study of the origin of words and the way in which their meanings have changed throughout history).