There are multiple meanings for "x train" depending on the context. Here are some of the most relevant ones:

• xTrain application: xTrain is an application used by program directors, principal investigators, university administrators, and trainees to electronically prepare and submit appointment forms for institutional research training grants and fellowships at the National Institutes of Health (NIH) .

• Cross training: Cross training, also known as "X-training", is an exercise regimen that uses several modes of training to develop a specific component of fitness.

• X-Train workout: X-Train is a 14-minute workout that focuses on the core, with a little upper and lower body to mix it up. The only equipment needed is a box or step for box jumps.

• X-Train party bus: The X-Train is a party bus that takes its name from a popular club drug. It has been known to cause disturbances in Kalamazoo, Michigan, such as ripping up lawns and scattering trash and broken glass along the streets.

In summary, "x train" can refer to an application used for submitting appointment forms for research training grants and fellowships at NIH, a type of exercise regimen, a specific workout routine, or a party bus in Kalamazoo, Michigan.