firstidea

noun
UK /ˌfɜːst aɪˈdɪə/
US /ˌfɝːst aɪˈdiːə/

The very first thought you have about something.

My firstidea for the school project was to build a volcano.


OTHER MEANINGS

2. The earliest plan made before any changes.

The firstidea was a treehouse, but we built a fort instead.

3. A beginning thought that starts a big project.

Her firstidea grew into a whole comic book series.

4. The thought you get before thinking more carefully.

His firstidea was to run, but he stayed and helped.