Medium Delirium

Graft / Grafted / Grafting
What it sounds like it means: To remove a portion/part of something
What it really means: To add to/ insert into something / to transplant one thing into another

Intrepid
What it sounds like it means: Timid and shy
What it really means: Fearless, particularly in having a taste for adventure

Will add to this list as and when I come across these oddities.