1. A plot of seismic events directly beneath the point midway between the source and detector locations. Such a section does not represent structural relationships correctly except where reflectors are flat. The vertical scale is usually either vertical time or depth (obtained by multiplying vertical time by average velocity). Often the same as a stacked CMP section or unmigrated section. 2. A plot of projections of seismic data showing where interfaces attributed to seismic events would intersect a vertical plane. Such a section is a correct structural section to the extent the picking, plotting, velocity, and projecting are correct. 3. A geologic cross-section showing structure. 4. The vertical versus stratigraphic thickness of a geologic unit.