black spot

Short definition from Wiktionary

Noun

1. 1
   A fungal disease among plants, particularly roses, that results in black spots on the leaves.
2. 2
   A section of roadway that has been designated as being particularly accident-prone.
3. 3
   A dangerous place or area.
4. 4
   A location with poor radio signal reception, e.g. for mobile phones.
5. 5
   A subject or area about which little or no information is available.
6. 6
   A fictional judicial device among pirates, consisting of a black circle indicating condemnation.
7. 7
   The spot on a snooker table where the black ball is normally placed.