Honest, especially in a manner that seems slightly blunt; candid; not reserved or disguised.
May I be frank with you?
Unmistakable, clinically obvious, self-evident
The research probes whether treating pre-diabetes with metformin can prevent progression to frank diabetes.
Unbounded by restrictions, limitations, etc.; free.
Liberal; generous; profuse.
Unrestrained; loose; licentious.
Somebody or something which franks.