Refers to a heraldic design used by a family or clan, similar to 紋 (もん). The term 紋標 is less common than 紋 alone.
See also: 紋
His family crest is a circle with three oak leaves.
playing card suit (in karuta)
Used specifically in the context of traditional Japanese card games like karuta to refer to the suit symbol.
The suits in karuta include cherry blossoms and plum blossoms.