What is the name of an allele combination where any young inherit this would die in the uterus?

You already name it:
Alleles that cause an organism to die are called lethal alleles, where the gene involved is an essential gene.

Example for your case with fur color:
Parents have black fur, both of them have the alleles for black and white fur: They are heterozygous for black and white. Black is dominant over white. The homozygous combination of BlackBlack is lethal.
Parents : Bw Bw
Children: BB Bw Bw ww
BB dies. Leaves us with 2 black and 1 white furred child.
I guess the word you are looking for is either 'homozygous' or 'essential gene'.

Interesting.  It's probably a 1:2:1 or a 3:1 ratio, but one of the homozygous combinations is the lethal.
I'm going to say that it's incomplete dominance for fur color, with the lethality following Mendelian dominance/recessiveness and the lethal combination being the recessive.