Step 1: Concept
Thermodynamic processes are often classified by the physical property that remains constant during the change.
Step 2: Meaning
The prefix "iso-" means same, and the term "baric" relates to barometric or pressure measurements.
Step 3: Analysis
1. Isothermal = constant temperature, 2. Isochoric = constant volume, 3. Isentropic = constant entropy, 4. Isobaric = constant pressure.
Step 4: Conclusion
An isobaric process is therefore defined as a process where the pressure of the system remains constant.
Final Answer: (B)