dictionary.com is a great website to look up definitions.
google.com
In the sentence 'Can you give a definition for that word?', YOU is the subject.
How can I give definition of this word? What is the definition of merc?
Onelook.com. Its a reverse dictionary website
dictionary.com
No, it is not a word. But if you give it a definition, you could make it a word...
The word is definition.
Definition.
Definition, (n) A description of the meaning of a word. That was an example.
you can go to dictionary.com
Google - online dictionary
boang ka