"Libra pondo"
Roman unit of weight

"Numero sign"
For ordinal numeration

£

"British pound sign"
Monetary abstraction

#

"Number sign"
See below...

Crosshatch, (garden) fence, mesh, flash, grid, pig-pen, tictactoe, scratch (mark), (garden) gate, hak, oof, rake, crunch, punch mark, sink, corridor, capital 3, and waffle.
via

how do you feel about using # (pound) for groups. As in #barcamp [msg]?

— Chris Messina 🏴‍☠️ (@chrismessina) August 23, 2007