Meaning

2 senses
  1. (UK, not comparable)Of a posture adopted by a person steering a vehicle (such as an aeroplane, car, or motorcycle): sitting up straight, not bent forward or leaning back.

  2. (UK, not comparable, specifically)Of a bicycle: having handlebars that are rather high and curve backwards, so that the rider sits upright rather than hunching forward; also, of the handlebars of a bicycle: rather high and curving backwards, thus requiring the rider to sit upright.

Origin

From sit up + and + beg, likening the position to a dog sitting up on its hindquarters and

From sit up + and + beg, likening the position to a dog sitting up on its hindquarters and begging by holding its front paws out.

Wiktionary, CC BY-SA 4.0 · source

See also

neighbours in the dictionary
sit-up-and-beg — meaning, examples, forms, synonyms | Krumeto