One is called a Guru if he grants one a mantra. Similarly, will one be called a Guru if the one teaches spiritual practice or meditation only? And Also, will the one who learnt spiritual practice from such teacher be considered as initiated?
Yes, one who teaches the spiritual disciples like- Yoga, Pranayama, meditation (which all have emerged from Parashiva) is also called a Guru.
The very 1st verse of Hatha Yoga Pradipika's 2nd chapter on Pranayama says:
अथासने दॄढे मोगी वशी श्चहतश्चभताशन् ।
गरूऩ श्चदष्टभागण प्राणामाभान्सभभ्यसत ॥ ् १॥
Athāsane drdhe yogī vaśī hitamitāśanah
Posture becoming established, a Yogî, master of himself, eating salutary and moderate food should practice Prânâyâma, as instructed by his guru.
Note the word Gurupadishta. Upadesha basically means instruction or advice and it usually applies to Mantra Diksha, but it also applies to the same regarding Yogic disciplines, as we can see from the above verse.
Another verse from the same text says:
सप्त गरु प्रसादन मदा जागश्चतत कुण्िरी ।
तदा सवाश्चत ण ऩद्माश्चन श्चबद्यन्ते ग्रन्थमोऽश्चऩ च ॥२॥
Suptā ghuruprasādena yadā jāgharti kundalī
Tadā sarvāni padmāni bhidyante ghranthayoapi cha
When the sleeping Kundalinî awakens by favor of a guru, then all the lotuses (in the six chakras or centers) and all the knots are pierced through.
So, without the Guru, success is not attained in Yogic disciplines as well. But, in scriptures, when they talk about Guru Diksha, then it means Mantra Diksha only.
And, similarly, the Siva Samhita states:
Now I shall tell you how easy to attain success in Yoga, by knowing which the Yogis never fail in the practice of Yoga.-10
Only the knowledge imparted by a Guru, through his lips, is powerful and useful; otherwise it becomes fruitless, weak and very painful. -11.
So, if someone is taught a Yogic disciple (like say Kriya Yoga) by a Guru personally, then it is quite alright to say that "he is being initiated by his Guru into Kriya Yoga".
Let me respond to this comment and also to the downvote cast.
A person who teaches meditation should have realized God, otherwise it is the blind leading the blind, and as the Upanishad says both falls into a ditch
This requirement is not limited to only the Guru who teaches Yogic disciplines. It is pretty much required for any Guru to be like that, more so for the Diksha Guru or the Mantra Guru.
Have a look at the following words of Lord Shiva:
Yas tattvavinmaheshAni sa pashum vodhayatyapi |
Tattva hinAt kutoha Adhyatma tattva gyAna parigrahah ||
O Consort of Mahesha, one who is self-realized (tattvavit) can help even a Pashu (the beast-like and the ignorant aspirant) to attain the state of realization; but how can one attain spiritual wisdom from one, who himself is unrealized (tattva hinAt)?
Kularnava Tantram 13.122
And here, Lord Shiva is talking about the Mantra Guru only.
Also, an etymological derivation of the word "Diksha" is given in the following verse:
DivyabhAba pradAnAccha kshAlanAt kalmashasya cha |
Diksheti kathitA sadvirbhava bandha vimochani ||
Because it gives the godly state of being (DivyabhAva), washes away (KshAlanAt) the sin and releases from the bonds of worldly existence, it is called DikshA.
KulArnava Tantram 17.51
So, Diksha is something that gives the Godly state (Divyabhava) of being and it removes sins as well (Papa Kshalanat). And, Yogic disciplines like meditation definitely are more potent in doing these two things than any others.
So, there is nothing wrong in calling a Yogic instruction an "initiation".
Now, a similar etymological derivation of the word Shishya is this:
Shariram artham prAnAmshcha sadgurubhyo nivedya yah |
Gurubhyoh shikshate yogam shishya itya bhidhiyate ||
Because he offers his body, wealth and life to the teacher's service, because he learns Yoga under his teacher, he is called the Shishya.
KulArnava Tantram 17.30.
So, one who teaches the Shishya, Yoga or meditation, is naturally called his Guru by the above derivation.
For example, the great Yogi Lahiri Mahashaya, was initiated into Kriya Yoga by Mahavatara Babaji and that's why the former is regarded as the disciple of the later.
Shyama Charan Lahiri (Bengali: শ্যামাচরণ লাহিড়ী Bengali: [Shêmā Chôron Lahiṛi]) (30 September 1828 – 26 September 1895), best known as Lahiri Mahasaya, was an Indian yogi and a disciple of Mahavatar Babaji. He was also popularly known as Yogiraj and Kashi Baba.