Effort, difficulty and hardship may be lexical descriptions of an activity. A term's defined usage in religious law is a different matter: it is a technical religious category.
The mere fact that an activity is difficult does not make it jihad in the specific sense under discussion. Treating every demanding activity as equivalent to that category erases the distinction between an ordinary word and a particular religious ruling.
The defined legal sense must therefore not be derived solely from the broad dictionary range.