adj

• (colloquial, regional British) In fairly good health.
  "I am in a middling Way, between Healthy and Sick, hardly ever without a little Giddineſs or Deafneſs, and ſometimes both: So much for that."

adv

• (colloquial, regional British) Fairly, moderately, somewhat.
  "St. Jerom ſeated, a middling ſized upright plate, from J. Palma, dated 1596. I think this is one of the fineſt prints by this great maſter. The drawing is admirable, and the engraving is executed with the utmoſt freedom."
• (colloquial, regional British) Not too badly, with modest success.

noun

• Something of intermediate or average size, position, or quality.
  "The war had been significantly financed by the poor and the middling, who purchased bonds that quickly devalued from wartime inflation; debt speculators had bought much of this debt at a fraction of the original cost."