From Wiktionary, the free dictionary
Text style
Emoji style
#︎
#️
Text style is forced with ⟨︎⟩ and emoji style with ⟨️⟩.
also #
A # used on a telephone keypad # (English symbol name number sign or hash or pound sign or octothorpe
( computing ) hash character. ( Internet ) hashtag , which is a metadata tag for use in microblogging and social network services, used to label and search content.
2019 June 27, Lisa Respers France, “Country star Jake Owen claps back at anti-LGBTQ commenter”, in CNN [1] “Some of my closest friends and coworkers, are part of the # lgbt community and I couldn’t be more happy for the progress they have made,” Owen wrote in the caption.
( cartography ) Used to denote a village . ( chess notation) Used to denote checkmate .
Synonym: ++ ( medicine , shorthand) Used to denote a bone fracture .
# NOFfractured neck of femur ( mathematics , computer science ) Used to indicate string concatenation .
1
#
2
=
12
{\displaystyle 1\#2=12}
( mathematics ) Apartness apartness relation .( mathematics ) Primorial Coordinate term: ! ( “ factorial ” )
12
#
=
2
×
3
×
5
×
7
×
11
=
2310
{\displaystyle 12\#=2\times 3\times 5\times 7\times 11=2310}
( set theory ) cardinality of a set.
#
{
5
,
3
,
7
,
11
}
=
4
{\displaystyle \#\{5,3,7,11\}=4}
Synonyms: card | | ( linguistics ) Used to indicate that a sentence is grammatical but semantically strange.
# Jane is a great hostess and John is too.
# I slept a wink last night.
# Colorless green ideas sleep furiously.
( phonology ) Used to indicate a word boundary.
d → t / _# ― /d/ devoices to [t] before a word boundary ( sign language linguistics ) Used to indicate a lexicalized sign. ( Usenet ) Used to pad the left side of a quotation from a manual or official source.
Coordinate term: > ( programming ) Used to indicate a hexadecimal color code.
#00FF00
bright green:
Alternative form of ‡ Alternative form of ⌗ ( “ key available on telephone keypads ” ) ( music ) Alternative form of ♯ ( “ sharp ” ) .Derived from the abbreviation lb Latin libra ( “ pound ” ) , via the medieval convention of indicating abbreviations with a bar, ℔
The pronunciation is usually that of its meaning; see pound number hashtag
# (plural # or #s
( US ) Pound (unit of weight ).
3# ― three pounds ( attributive , precedes a numeral) Number .
Synonym: no. # 3number three( Internet slang , text messaging ) Number .
1986 December 14, Ben Robbins, “Operator Denies Request For Gay Phone # ”, in Gay Community News , volume 14 , number 22 , page 2:
1997 June 17, RYankowski [ username] , “Why collect new U.S.?”, in rec.collecting.stamps [2] Usenet ):I have collected U.S. Stamps since I was a boy back in the 1950's. At that time there was a low # being printed and it was affordable.
( informal , preceding a phrase) Hashtag .( Scrabble ) In English-language Scrabble word list and not the North American list.
#
( Mainland China ) alternative form of 號 / 号 ( “ number ” ) , used after a numeral. 
Number sign on Wikipedia.Wikipedia 