Here is a Keyboard Maestro macro to goto the next segment and query all active web resources.
Note that you have to redefine the keyboard shortcut to go to the next segment to Alt+Down, see the CafeTran Preferences.
Possible improvement: test for presence of any white space, number, tag or punctuation character and only perform the filtering part if any of them is present.
Reasoning from the perspective of the online dictionary (so actually quite the other way around as you are pointing out–to which I agree, of course): a setting/field in the web resource 'Number of words per query' could be useful.
Langenscheidt: one word at at time
IATA: multiple words are allowed
And then there's probably need for an extra field in this web resource definition to indicate how spaces are coded: %20 or + or ...