black spot

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