(transitive, reflexive, obsolete) Keep or withhold oneself.
(intransitive) Refrain from (something or doing something); keep from doing, especially an indulgence.
In order to improve his health, Rob decided to abstain from smoking.
The Security Council […] calls upon all Governments and authorities, without prejudice to the rights, claims or positions of the parties concerned, to abstain from any hostile military action in Palestine and to that end to issue a cease-fire order to their military and paramilitary forces
(intransitive, obsolete) Fast (not eat for a period).
(intransitive) Deliberately refrain from casting one's vote at a meeting where one is present.
I abstain from this vote, as I have no particular preference.