adamant
AD-uh-muntadjMeaning firmly insisting; refusing to be talked out of something
Memory hook a NO as hard as a DIAMOND. Pip begs to have cake for breakfast, but Granny Mae’s “no” is as hard as a diamond: she is adamant. (Diamond and adamant come from the same Greek word, adamas.)
Grandpa was adamant that we wear our seat belts, even for a one-block drive.
In context The class begged for one more week to finish their projects, but the teacher was adamant: the deadline was Friday, and no pleading would change it.
Similar insistent, unyielding, firm, unshakable
Opposite flexible, yielding, wavering
From an old noun adamant, a stone once believed to be unbreakable, from Greek adamas, “unconquerable.”