/help levels 

05:10 Message levels (or in short, levels) are used almost everywhere. They describe what kind of messages we're dealing with. Here's a list of them all:
05:10 
05:10     CRAP            - Can be almost anything
05:10     MSGS            - Private messages
05:10     PUBLIC          - Public messages in channel
05:10     NOTICES         - Notices
05:10     SNOTES          - Server notices
05:10     CTCPS           - CTCP messages
05:10     ACTIONS         - Actions (/me) - usually ORed with PUBLIC or MSGS
05:10     JOINS           - Someone joins a channel
05:10     PARTS           - Someone parts a channel
05:10     QUITS           - Someone quits IRC
05:10     KICKS           - Someone gets kicked from channel
05:10     MODES           - Channel mode is changed
05:10     TOPICS          - Channel topic is changed
05:10     WALLOPS         - Wallop is received
05:10     INVITES         - Invite is received
05:10     NICKS           - Someone changes nick
05:10     DCC             - DCC related messages
05:10     DCCMSGS         - DCC chat messages
05:10     CLIENTNOTICE    - Irssi's notices
05:10     CLIENTERROR     - Irssi's error messages
05:10     CLIENTCRAP      - Some other messages from Irssi
05:10 
05:10 And a few special ones that could be included with the levels above:
05:10 
05:10     HILIGHT         - Text is highlighted
05:10     NOHILIGHT       - Don't check highlighting for this message
05:10     NO_ACT          - Don't trigger channel activity when printing
05:10                       this message
05:10     NEVER           - Never ignore or log this message


/help ignore 

05:12 IGNORE [-regexp | -full] [-pattern <pattern>] [-except] [-replies] [-network <network>] [-channels <channel>] [-time <secs>] <mask> [<levels>]
05:12 IGNORE [-regexp | -full] [-pattern <pattern>] [-except] [-replies] [-network <network>] [-time <secs>] <channels> [<levels>]
05:12 
05:12     -regexp: <pattern> is a regular expression
05:12     -full: <pattern> must match to full words
05:12     -pattern: <pattern> must match to the message's text
05:12     -replies: Ignore replies to nick in channels. For example
05:12               "/IGNORE -replies *!*@*.fi PUBLIC" ignores everyone
05:12               from Finland, but also anyone sending message
05:12               "tofinnishnick: blahblah".
05:12     -except: *DON'T* ignore - overrides an existing ignore.
05:12     -network: Ignore only on this network.
05:12     -ircnet: Same as -network. Deprecated. Do not use.
05:12     -channels: Ignore only in channels
05:12     <mask>: Either a nick mask or list of channels
05:12     <levels>: List of levels to ignore. You can use -<level> to remove levels
05:12               from ignore.
05:12     <^levels>: List of levels to NOT ignore
05:12                (/ignore -except nick notices = /ignore nick ^notices)
05:12 
05:12 
05:12 /IGNORE without any arguments displays list of ignores. If you want to remove some levels of the ignore, use /IGNORE <mask> -<level> -<level2> etc
05:12 
05:12 The best match always wins, so you can have:
05:12     /IGNORE * CTCPS
05:12     /IGNORE -except *!*@host.org CTCPS
05:12 
05:12 Examples:
05:12 
05:12     /IGNORE #channel ALL -PUBLIC -ACTIONS   - ignore all but public/actions
05:12     /IGNORE #channel -JOINS                 - don't ignore joins anymore
05:12     /IGNORE -replies *!user@*.host.org ALL  - ignore user and all replies
05:12 
05:12 Some suggestions for ignoring annoying public aways:
05:12     /IGNORE -regexp -pattern "is (away|gone|back)" * ACTIONS
05:12     /IGNORE *zzz* NICKS
05:12     /IGNORE *afk* NICKS
05:12     /IGNORE *away* NICKS
05:12 
05:12 For regular expressions, see `man 7 regex`.
05:12 
05:12 See also: UNIGNORE, SILENCE, ACCEPT