noun
ōyamafuda (competitive karuta); the six cards with six-mora kimariji
In competitive karuta (kyōgi karuta), the six cards whose kimariji (決まり字) are six mora long. These are the hardest to take quickly because the unique identifying part is long.
See also: 決まり字 (きまりじ)
大山札は決まり字が長いので、試合では特に集中力が必要だ。
Because the ōyamafuda have long kimariji, they require extra concentration in a match.