Half-cousin or half-1C:
1- Parent's half-sibling's child.
2- Person who, in relation to the other person, has zero parents and one grandparent in common.
Half-2C:
1- Parent's half-first-cousin's child.
2- Grandparent's half-sibling's grandchild.
3- Person who, in relation to the other person, has zero parents, zero grandparents and one great-grandparent in common.