sidelong
Directed to the side; sideways.
He cast me a sidelong glance.
Slanting or sloping; oblique.
Indirect; suggestive; not straightforward.
She made some sidelong remarks about his manhood.
Along the side of something.
The passenger train was signalled from one of the west end bay platforms along the Down South Line; as it passed through a crossover to the Up South Line the freight train, which had been travelling slowly to the Up South Line, over-ran the signal protecting the crossover and came into sidelong collision with it.
Where it comes from
1520s, from Middle English sidlyng (early 14th century), from side + -lyng (“(frequentative)”) (modern English -le (“(frequentative)”)). Reanalyzed as side + long.
Adapted from the Wiktionary entry sidelong (CC BY-SA 4.0).