Definitions for "Heterogeneous nuclear RNA"
RNA products immediately synthesized from the DNA template in the nucleus (sometimes called DNA-like RNA or dRNA). This RNA species has a short half-life, is very heterogeneous and very large (molecular weight in excess of 107). hnRNA molecules are processed to generate the mRNA molecules (molecular weight generally less than 2x106) before leaving the nucleus.
(hnRNA)  Large RNA molecules, which are unedited mRNA transcripts, or pre-mRNAs found in the nucleous of a eukaryotic cell. See RNA.
(hnRNA) RNA transcripts in the nucleus, representing precursors and processing intermediates of rRNA, mRNA, and tRNA, as well as mature RNA transcripts not yet transported into the cytoplasm.