You can query Wikipedia from the command line using dig .

For example,

dig +short txt monkey.wp.dg.cx

will return

“A monkey is a nonhuman primate mammal with the exception usually of the lemurs and tarsiers. More specifically, the term monkey refers to a subset of monkeys: any of the smaller longer-tailed catarrhine or platyrrhine primates as contrasted with the apes.” “ http://en.wikipedia.org/wiki/Monkey”

The command is a little fiddly to remember, so you could wrap it up in a shell function, like so

wiki() { dig +short txt $1.wp.dg.cx }

then type

wiki monkey

to view a quick definition and the URL to the Wikipedia article in question.