The definition of exocentric is two or more parts of a phrase that are different parts of speech and, when combined, form another part of speech which is different from all of the parts.
An example of an exocentric construction is when a noun is combined with a verb phrase to form a sentence; Mr. Lincoln (a noun) came to Washington (a verb phrase).
Of or relating to a group of syntactically related words, none of which is functionally equivalent to the function of the whole group. For example, none of the words in the phrase on the table is an adverb, yet they combine to form a phrase having adverbial function.
Of or relating to a compound word whose referent is not the same as the referents of any of its constituent parts. For example, the noun razorback does not refer to a type of back, but to a type of hog (one having a sharply ridged back).
Designating or of a construction whose syntactic function is different from that of any of its constituents (Ex.: all the way in the sentence “he ran all the way”)