The reaction that does NOT define calcination is :

Options

A. `CaCo_(3) . Mg CO _(3) overset(Delta) to CaO + MgO + 2CO_(2)`
B. `2 Cu S + 3O_(2) overset(Delta) to 2Cu _(2)O+ 2SO_(2)`
C. `Zn CO_(3) overset(Delta) to Zn O + CO_(2)`
D. `Fe _(2) O _(3). XH_(2) O overset(Delta) to Fe _(2) O _(3) + XH_(2) O `

Explanation

To determine which reaction does NOT define calcination, we first need to understand what calcination is. Calcination is a thermal treatment process that involves heating a substance to high temperatures in the absence of air or oxygen, typically to remove volatile substances or to drive off carbon dioxide from carbonate ores.

### Step-by-Step Solution:

1. **Understanding Calcination**:
- Calcination primarily involves the thermal decomposition of carbonate ores (like calcium carbonate, CaCO3) into oxides (like calcium oxide, CaO) and carbon dioxide (CO2).
- It can also involve the heating of certain metal oxides.

2. **Analyzing the Options**:
- **Option 1**: CaCO3 → CaO + CO2
- This reaction is a classic example of calcination as it involves the decomposition of calcium carbonate into calcium oxide and carbon dioxide.
- **Option 2**: CuS + O2 → Cu + SO2
- This reaction involves the roasting of a sulfide ore (copper sulfide) in the presence of oxygen, which is not calcination. This process is known as roasting, not calcination.
- **Option 3**: MgCO3 → MgO + CO2
- Similar to option 1, this reaction involves the decomposition of magnesium carbonate into magnesium oxide and carbon dioxide, which is also a calcination process.
- **Option 4**: ZnO + heat → Zn + O2
- This reaction involves heating zinc oxide, which can be part of a calcination process, although it is more commonly associated with reduction.

3. **Conclusion**:
- From the analysis, option 2 (CuS + O2 → Cu + SO2) does NOT define calcination as it describes the roasting of a sulfide ore in the presence of oxygen.

### Final Answer:
The reaction that does NOT define calcination is: **Option 2: CuS + O2 → Cu + SO2**.