Cad, bounder, rotter mean one who shows himself to be no gentleman. Usually they are somewhat vague terms of contempt for bad behavior or manners.
By, through, with are comparable as prepositions followed by a word or phrase naming the agent, means, or instrument.
Buy, purchase mean to acquire something for money or an equivalent.
Buttress, pier, abutment are architectural terms for auxiliary structures designed to serve as a prop, shore, or support for a wall (as of a building).
Busy, industrious, diligent, assiduous, sedulous mean actively engaged or occupied in work or in accomplishing a purpose or intention.
Business, commerce, trade, industry, traffic are comparable chiefly when they denote one of the forms or branches of human endeavor which have for their objective the supplying of commodities.
Burn, scorch, char, sear, singe mean to injure by exposure to fire or intense heat.
Burden, encumber, cumber, weigh, weight, load, lade, tax, charge, saddle are comparable when they mean to lay a heavy load upon or to lie like a heavy load upon a person or thing.
Bundle, bunch, bale, parcel, pack, package, packet denote things done up for storage, sale, or carriage.
Bump, clash, collide, conflict are comparable when they mean to come or cause to come into violent contact or close or direct opposition.