This word appears in Chapter Ten of Wuthering Heights when Nelly Dean explains to Lockwood how she reluctantly left Wuthering Heights to go to Thrushcross Grange with Catherine when she married Edgar Linton. She did not want to leave Hareton, especially because of the way in which Hindley was becoming increasingly dissolute, but her mistress insisted, and Catherine went to both her husband and brother to aid her in persuading Nelly to leave Wuthering Heights:
When I refused to go, and when she found her entreaties did not move me, she went lamenting to her husband and brother. The former offered me munificent wages; the latter ordered me to pack up: he wanted no women in the house, he said, now that there was no mistress...
Edgar Linton therefore offered Nelly "munificent wages," meaning wages that are generous or bountiful, as part of his attempt to entice Nelly to join his new wife in Thrushcross Grange.
Munificent means to characterized by great generosity so as Accessteacher said, Edgar offered Nelly bigger wages to try and convince her to join Cathy at his house, Thrushcross Grange.