Spiritual friendship... can be someone on the same spiritual
path as you and offer support and companionship on the path to
Buddhahood.
An excerpt from Sigolavada Sutta on 'worthy friends':
http://www.accesstoinsight.org/tipitaka/dn/dn.31.0.nara.html
"These four, young householder, should be understood as
warm-hearted friends:
(1) "In four ways, young householder, should a
helpmate be understood as a warm-hearted friend:
(2) "In four ways, young householder, should
one who is the same in happiness and sorrow be understood as a
warm-hearted friend:
(3) "In four ways, young householder, should
one who gives good counsel be understood as a warm-hearted
friend:
(4) "In four ways, young householder, should
one who sympathises be understood as a warm-hearted friend:
Thus spoke the Exalted One. And when the Master had thus spoken,
he spoke yet again: