beginners question

[Heli Friend]

wat is the meaning of boomstrike.

[yC86]

arr.... when the blades lead/lag (fold back/front) n wack the boom

[9VDXN]

you'll know it when it happens suddenly due to your own foolishness, and you realised that you have to:
1) Change tail boom
2) Change main rotors
3) waste a lot of money
4) and promise yourself not to make that silly mistake...