Meaning

1. An almost transparent aquatic animal; any one of the acalephs, especially one of the larger species, having a jellylike appearance.
2. An almost transparent aquatic animal; any one of the acalephs, especially one of the larger species, having a jellylike appearance.
3. An almost transparent aquatic animal; any one of the acalephs, especially one of the larger species, having a jellylike appearance.
4. A sudoku technique involving possible cell locations for a digit, or pair, or triple, in uniquely four rows and four columns only. This allows for the elimination of candidates around the grid.