If you have a cell-array of words you want to check, you should use ismember. So, if you had a dictionary array dict and a set of words words, you would use
check = ismember(words,dict);
where check would be something along the lines of [0,1,1], if the first word wasn't in the dictionary, but the other two were.
EDIT:
I guess that dictionary is a function? Sorry, I didn't pick up on that the first time around. In that which case, borrowing from this answer to a different question, you can do the following:
dict_fun = @(word,trash)dictionary(word);
check = bsxfun(dict_fun,nchoosek('london',3),1);