Answer:
Belt:
A belt is a "band of material" that is typically worn around the waist.
I unbuckled my belt as I came back from work, eager to unwind after a tiring day.
Shuttle:
A shuttle is a transportation vehicle that goes from one place to another, back and forth.
I climbed aboard the shuttle after realizing that my car was out of gas and this was my only option to get to work on time.
Network:
A "system" of lines/wires that connect to each other.
Many people toiled for months and months to ensure that the rail network would be ready for trains at the given date.
Since you didn't enclose the poem you are referring to, I cannot use the same definitions from it. I did, however, use definitions from the site you gave.
Hope this helps! <3