An eligible 401k Rollover distribution from a participant's (or a deceased participant's spouse) employer's qualified pension, an IRA rollover from a profit-sharing or stock bonus plan, an IRA rollover from a qualified annuity plan, or tax-sheltered annuity plan (403b plan) or governmental 457 plans, can be rolled over, all or in part into a traditional IRA. This can be referred to as a traditional IRA rollover.
401k_Rollover.html
Usually it is more common to see a 401k rollover into an IRA. However, occasionally, there are needs for an IRA rollover into a 401k or other qualified retirement plans.
This can be done. But the rules depend on the accepting retirement plan.
Starting in 2002, an IRA retirement plan owner can roll over, tax free, a distribution from an IRA into a qualified plan, 401k,and other retirement plans including a section 457 plan and a tax-sheltered annuity (section 403b plan).
IRA_Rollover_into_401k.html
Can I do a 401k transfer? Absolutely, 401k transfer can be done. A 401k transfer is usually initiated when you are leaving your job.
401k_Transfer.html