How to delete a subkey on Linux in GnuPG?

I would like to delete an OpenPGP subkey of mine on Linux (L)Ubuntu 16.04 in GnuPG. It's a kind of "blank" useless key (see below key 33333333). I have not uploaded it to key servers, so I think it's ok to delete without revoking it.

gpg2 --edit-key [email protected]

sec  rsa4096/11111111
     created: 2016-12-12  expires: 2017-12-12  usage: SC  
     confiance : ultime        validity: ultimate
ssb  rsa4096/22222222
     created: 2016-12-12  expires: 2017-12-12  usage: E   
ssb  rsa4096/33333333
     created: 2016-12-12  expires: never       usage:     
ssb  rsa4096/44444444
     créé : 2016-12-12  expires: 2017-12-12  usage: S   
[  ultimate ] (1). me <[email protected]>

I tried "gpg> delkey 33333333", but I had this message :

You must select at least one key.
(Use the 'key' command.)

then gpg> key 33333333, and I had this result (same result as list command):

sec  rsa4096/11111111
     created: 2016-12-12  expires: 2017-12-12  usage: SC  
     confiance : ultime        validity: ultimate
ssb  rsa4096/22222222
     created: 2016-12-12  expires: 2017-12-12  usage: E   
ssb  rsa4096/33333333
     created: 2016-12-12  expires: never       usage:     
ssb  rsa4096/44444444
     créé : 2016-12-12  expires: 2017-12-12  usage: S   
[  ultimate ] (1). me <[email protected]>

What should I do next?

GnuPG's interactive --edit-key menu works differently. You do not select a subkey by key [subkey-id], but by key [key-index], in your case this would be key 2 (the second subkey from the top, the primary key doesn't count).

After doing so, the line

ssb  rsa4096/33333333

will change to

ssb* rsa4096/33333333

with an asterisk indicating the key being selected. After selecting one or more keys, run delkey to delete the selected subkeys. Don't forget to save!