A half note that has at least one dot placed to the right of it. The dot denotes that the note's length is increased by half of its original value. In general, a note can have up to three dots. Subsequent dots add progressively halved value.
You can see one right at the top of the image in post #291902.
Not to be confused with staccato, where the dot is placed above or below a note.
The following tags are aliased to this tag: dotted_minim (learn more).