Though I based my definition from a dictionary, my definition to the term would be my own.
Bus in our transport industry is a vehicle that is used to transport passengers. It travels in a road or highway. The transport time of the passagers or cargo is relative to the bus's speed.
In computer terminology, bus still conveys the meaning of transport but it is no longer the vehicle; its the highway in which the data travels. A 32-bit bus can be pictured as a 32-lane highway. That highway can transport/transmit 32 bits of data simultaneously at a given time.
So you see, the data transported is not in paragraphs or words; its in bits. Bit is the contracted form for "binary digit", the language of the computer. A single character, be it a letter or a number, comprises eight (8) bits. So a 32-bit bus can transport barely four characters simultaneously at a given time. The greater the width of the bus/highway, the better the performance.
Can you imagine how long will a single paragraph of information be processed from the keyboard input, to the memory, to the processor, then back to the memory again, to the disk, then lastly to the printer? Thanks God for ultra fast processors we have in our computers nowadays.
Another factor is the bus speed, presently measured in MHz. The faster the bus speed, the better the performance.
That's all as far as the computer's bus is concerned.
Let's now talk of the USB. The USB is an external bus standard that can support data transfer rate of 12Mbps. The storage device we commonly use to connect to the USB port is also called USB. But the USB port can be used to connect up to 127 diffrent peripheral devices including mouse, modem, or printer.
Lastly, you may think that USB is the best there is nowadays but that may be wrong. To me USB is second only to USA.