A large stone that lies above a grave. The tomb stone usually has the name of the deceased, their year of birth/death, and more information about the person, such as their family or an achievement while they were alive (ex: Here lies Sam "Pull" Text 1990-2024 A loving brother, father, son, husband R.I.P. (short for rest in peace)).
For a grave marker that is in the shape of a cross, use memorial cross instead. For a grave marker that features a cross as one part, but not the entirety, of its design, use tombstone