If you describe an object, idea, or course of action as impractical, you mean that it is not sensible or realistic, and does not work well in practice.
Once there were regularly scheduled airlines, it became impractical to make a business trip by boat.
一旦有了定期的航班,乘坐客轮出差就变得不切实际了。
If you describe someone as impractical, you mean that they do not have the abilities or skills to do practical work such as making, repairing, or organizing things.
Geniuses are supposed to be difficult, eccentric and hopelessly impractical.
天才被认为很难相处、行为怪僻且毫无实际能力。