It's probably a distribution of income, for tax accounting purpose -- that is, determining distributable net income (DNI).  The distinction between principal and income is more of a trust accounting concept.  It's probably a second-tier distribution, shown on Line 10, Schedule B of the 1041, but we really don't have enough information here to know.   For example, 

"A specific bequest is not considered a taxable distribution to the beneficiary if it is a distribution of a specific property or a specific sum of money. These distributions do not carry out income to the beneficiary and they generate no income distribution deduction to the estate or trust."

For further pitfalls and loopholes, see

http://www.cchwebsites.com/preview/36/369ce1d22cf8247c13bff0428abed604/content/client/369ce1d22cf824...