The definition is in the text.
Forage:
Night is the time when many animals forage, or search, for food.
Search for food
Injustice:
Kevin thought it was a great injustice that his older brother could have a phone but he could not.
Lack of fairness
Current:
The current is strong in this part of the river.
"a body of water or air moving in a definite direction, especially through a surrounding body of water or air in which there is less movement."
Erudite:
One brother is an erudite, or very knowledgeable, professor.
Very knowledgeable
Splendidly:
The rays of the sun shone splendidly through the window.
In a magnificent or impressive way.
Certain:
He was certain that his own opinion was right.
"having complete conviction about something; confident."
Altruism:
Psychologists have conducted research on altruism, which can be defined as "putting the needs and welfare of others above one's own needs and well-being."
Putting the needs and welfare of others above one's own needs and well-being
Elegant:
Cassie shopped for an elegant gown for her sister's wedding.
Hamper:
Don't let the rain hamper your plans.
"hinder or impede the movement or progress of."
Cutlery:
The store specializes in cutlery, such as forks and knives, that has unique designs.
Particle:
John was so hungry he didn't leave a single particle of the muffin on his plate.
Prune:
An apple tree grows better when you prune it.
"to cut off or cut back parts of for better shape or more fruitful growth."
Brusque:
The waiter was so brusque that we left only a small tip. He was impolite and impatient, and seemed annoyed whenever we asked for something.
Impolite and impatient
Decline:
After the restaurant's new owners who got rid of the most popular meals, the customers started to decline.
Become smaller or fewer
Refrain:
The choir sang the refrain again.
"A repeated line or number of lines in a poem or song, typically at the end of each verse."