The Hebrew word beosh means stench or foul odor — the putrid smell of decaying matter. It derives from the root baash (H887), meaning to stink or emit a foul odor, used literally for spoiled food and metaphorically for moral corruption.
The imagery of stench in the Old Testament is regularly used to describe the state of those who have abandoned covenant faithfulness. When the Egyptians' water turned to blood, there was a stench (Exodus 7:18). When Israel was oppressed, their situation stank in the nostrils of their oppressors. The prophets used olfactory language to describe moral rottenness (Amos 4:10). Paul, conversely, describes believers as a 'pleasing aroma of Christ' to God (2 Corinthians 2:15–16). Holiness has a fragrance; sin has a stench — a visceral reminder that God's moral categories are as real as physical senses.