Abarim Publications' online Biblical Hebrew Dictionary
The verb חפז (hapaz) expresses a combination of being afraid and taking flight: to be prone to run off (Deuteronomy 20:3, 2 Kings 7:15, Psalm 31:22). In 2 Samuel 4:4, the nurse of five year old Mephibosheth is in the state that this verb describes and drops the child, because of which he becomes "lame (פסח, piseah) in both feet", which probably means that he stayed childlike.
Our verb has one derivative, namely the masculine noun חפזון (hippazon), which describes the state of trepidation in combination with the readiness to take to hurried flight. This noun is always preceded by the preposition ב (beth), meaning in.
Our noun is used three times. Twice as the prescribed mindset or attitude that people are to assume while gobbling down the Pesah meal (Exodus 12:11, Deuteronomy 16:3; possibly meaning that people are to assume childlike trepidation), and once in a prophecy of Isaiah, when this sort of mindset is declared to have become obsolete (Isaiah 52:12).