lacking: short of something needed, in want of it, or deprived of it
At its core this word simply marks a shortfall: someone or something is short of what it needs, deprived of it, or without it. It rarely stands alone. It usually attaches to whatever is missing, and that missing thing sets the tone: when food is lacking it means physical want, and when good sense is lacking it means folly.
By far its most frequent home is the book of Proverbs, where the phrase "lacking heart" becomes a fixed label for the fool. In Hebrew the heart is the seat of thought and judgment, not the emotions, so the fool is the person short on the sound judgment a mature mind should have. This is not a claim that he has no feelings; it is a claim that his thinking is deficient.
The same adjective also covers plain material lack, such as a household short of bread, and general want, such as having gone without nothing or needing something one does not have. The related noun מַחְסוֹר names that state of need as a thing in itself, while this word describes the person or situation that falls short.