Both Uses of

prodigal
in
Middlemarch

But he would never lose sight of her: he would watch over her—if he gave up everything else in life he would watch over her, and she should know that she had one slave in the world, Will had—to use Sir Thomas Browne's phrase—a "passionate prodigality" of statement both to himself and others.†
Chpt 4

For my own part, I regretted your alliance with my brother-in-law's family, which has always been of prodigal habits,
Chpt 7 *

prodigal = recklessly wasteful

Definitions:

(1) (prodigal)
recklessly wasteful

or more rarely:

abundant (extravagant in amount)

or more rarely still:

long absent (someone who has been away a long time)
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely, prodigal is used as a noun as a shortened version of prodigal son to reference someone who is wasteful like the prodigal son in the famous Christian parable. When the prodigal son came home and apologized for his wasteful and ungrateful ways, his father forgave him, loved him, and celebrated the return.