1) The business or occupation of getting out various kinds of lumber, such as timber, boards, staves, &c. 'To go a lumbering,' is the phrase used by those who embark in it.
2) Strolling, lounging, walking leisurely. A vulgarism used in New York.
As I was lumbering down the street, down the street,
A yaller gal I chanc'd to meet, etc.--Negro Melodies. The Buffalo Gal.