Stride Piano

"Stride piano" is well described in Posnak's preface (explanations in brackets are mine) "The oom-pa left hand of ragtime was expanded to wide leaps between main-beat bass notes and weak-beat chords, often jumping two or more octaves. Single-note and octave bases were often replaced by tenths or filled-in tenths[that is, with a fifth thrown in]--a bigger sound (for big hands) at a faster tempo [than ragtime]. The left-hand tenth developed a life of its own, ofter "streaming" in parallel instead of striding [that is, instead of alternating between a low bass note on 1 and 3 and a chord on 2 and 4, there will be a series of four tenth chords progressing up one note at a time], sometimes starting with the upper-note thumb instead of the bass-note fifth finger ("backwards tenths"), sometimes mixing it up on the main and secondary beats...Meanwhile, the right hand was free up to cut figure eights around the melody, with brilliant passagework [sequences of chords leading from one key to another], combinations of single-and double-note riffs, chords, and melodic improvisation, often at cross-rhythm [i.e., with varying syncopations] with the steady, driving left hand."

More information and opinions about what stride piano is (and is not) can be found here. And here is a page on the history of stride piano.