It's QDRO and it stands for Qualifed Domestic Relations Order. It's a court order that has to be approved by the retirement system's plan administrator to be enforceable against the plan (QDROs are the product of federal law) and they are required to divide a marital interest in a retirement plan- a private pension plan, 401(k) and so on. If you want your share of hubby's retirement, you have to have a QDRO to do it if it is a private employer (we have QDRO-like orders in government retirement plans that are very similar but not subject to the federal law that applies to QDROs, which is called ERISA [the Employees Retirement Income Security Act of 1974] and REA, the Retirement Equity Act).
A 401(k) is a deferred compensation retirement account or more correctly, a defined contribution retirement plan. You need a QDRO to divide them just like with a pension plan. Usually a specialist (called an actuary) prepares the QDRO or an attorney experienced in their preparation (it's a kind of speciality almost) and the cost varies from place to place but often runs about $500 in California. If you check online you can find several people able to do them.
If you are recently divorced, don't wait to get the QDRO in. If your ex were to die before the QDRO were submitted to the plan you could lose your rights to your share of the 401(k) even if the divorce decree grants you a portion of it. Don't delay. Trust me on this.