Abarim Publications' online Biblical Hebrew Dictionary
The verb לאה (la'a) means to be weary, grieved, offended (even impatient or slow says BDB Theological Dictionary). HAW Theological Wordbook of the Old Testament sums the meaning of this verb up as, "physical or psychological weariness". It may occur to someone who runs with footmen (Jeremiah 12:5), or folks who vainly try to find a way into a house (Genesis 19:11). It may happen when water has a disagreeable taste (Exodus 7:18) or when a person is so lazy that the mere effort of bringing food to his mouth wears him out (Proverbs 26:15).
This verb's sole derivation is the feminine noun תלאה (tela'a), toil, hardship (Exodus 18:8, Nehemiah 9:32).