Astride is an adverb that describes a verb has having been accomplished with legs spread apart, or one leg on either side of something. One can stand or ride a horse astride. The word can also act as a preposition where it adds another definition. It can mean to spread across something. A good synonym is span or bridge.
This term is mostly associated with horses, and often the phrase legs apart would be clearer.
How big is the blind spot that allows you to occupy seats of such cultural privilege, but nevertheless to run around sniveling about how it’s not actual minorities who are oppressed, but you — sitting astride your cultural warhorses — who are truly imperiled? [The Huffington Post]
In Bejing on Friday, Foreign Ministry spokeswoman Hua Chunying said China advocated talks to resolve tensions between rival claimants to islands in the South China Sea, where island groups sit astride some of the world’s busiest shipping lanes and potentially huge mineral reserves. [The Washington Times]
Astride the snowmobile, Tom Seaton, a wildlife biologist for the state of Alaska, led the way through the wilderness. [Los Angeles Times]
The closest I come to my hero, Jackie Chan, is when we adopt the Lower Horse Stance, squatting down on my haunches, legs astride with arms outstretched. [The Telegraph]
Kala Ghoda used to house the statue of King Edward VII astride a horse, which has long vanished, the name remains and this area synonymous with the annual open-air art shows held every February. [The Gleaner]