The free online version of the Oxford has 2 definitions. See [link|http://www.askoxford.com/results/?view=dict&field-12668446=impose&branch=13842570&textsearchtype=exact&sortorder=score%2Cname|http://www.askoxford...rder=score%2Cname]. The one that applies here is clearly force to be accepted, undertaken, or complied with.

Merriam-Webster's online dictionary has 4 definitions. See [link|http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=impose&x=0&y=0|http://www.m-w.com/c...va=impose&x=0&y=0]. The first is the one that applies, and it comes in 2 forms. a : to establish or apply by authority <impose a tax> <impose new restrictions> <impose penalties> b : to establish or bring about as if by force <those limits imposed by our own inadequacies -- C. H. Plimpton>.

Dictionary.com has 5 definitions. See [link|http://dictionary.reference.com/search?q=impose|http://dictionary.re...m/search?q=impose]. The first 2 could apply, and are essentially the same as Merriam-Webster's definitions.

Note that part of mastering English is not just being able to recite definitions out of the dictionary, it is having a good enough understanding of how language is used to know which definition is meant.

Regards,
Ben