Define
Vine's Expository Dictionary of NT Words [1]
(Eng., "horizon"), primarily means "to mark out the boundaries of a place" (as in the Sept. of Numbers 34:6; Joshua 13:27 ); hence "to determine, appoint." In Hebrews 4:7 , where the reference is to the time of God's invitation to enter into His rest, in contrast to Israel's failure to do so, the word may mean either the appointing of the day (i.e., the period), or the "defining" of the day, i.e., marking its limits. So the RV (AV, "limiteth"). See Declare , Determine , Limit , Ordain.
Webster's Dictionary [2]
(1): ( v. t.) To fix the bounds of; to bring to a termination; to end.
(2): ( v. i.) To determine; to decide.
(3): ( v. t.) To determine the precise signification of; to fix the meaning of; to describe accurately; to explain; to expound or interpret; as, to define a word, a phrase, or a scientific term.
(4): ( v. t.) To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly; as, the defining power of an optical instrument.
(5): ( v. t.) To determine or clearly exhibit the boundaries of; to mark the limits of; as, to define the extent of a kingdom or country.