Definify.com

Webster 1913 Edition

(lĕjˊĭ-bĭl′ĭ-ty̆)

Noun.

The quality of being legible; legibleness.

Sir. D. Brewster.

Noun.

Legibleness; the quality or state of being legible.

legibility ‎(countable and uncountable, plural legibilities)

The property of being legible or easily readable.
The legibility of this text is questionable: half the people asked said it was almost illegible, but the other half said it was easy to read.

property that makes legible or easily readable