You can prevent Spotlight from showing dictionary results by typing the following into Terminal:

defaults write com.apple.spotlight DictionaryLookupEnabled NO

The same goes for calculations:

defaults write com.apple.spotlight CalculationEnabled NO

Note that for either of these changes to take effect, you need to restart Spotlight. Use Terminal to do so:

sudo killall

 Spotlight

I’m not certain why anyone would want to disable either of those features, but it is possible.

[robg adds: To reverse either of these settings, repeat the commands but replace NO with YES, soon after kill Spotlight again.]

Original post by Michael Rose